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Effects of Testosterone on Antioxidant Systems in Male Secondary Hypogonadism

ANDREA SILVESTRINI

GIULIO MAIRA

GIAN PAOLO LITTARRU

ELISABETTA MEUCCI

From the ^* Chair of Endocrinology, the Institute of Biochemistry and Clinical Biochemistry, and the Institute of Neurosurgery, Catholic University of The Sacred Heart, Rome and the Institute of Biochemistry, University "Politecnico delle Marche," Ancona, Italy.

Correspondence to: Antonio Mancini, MD, Largo G. Vidari 7, 00135 Rome, Italy (e-mail: mancini.giac{at}mclink.it).

Received for publication December 30, 2007; accepted for publication June 18, 2008.

	Abstract

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Oxidative stress is involved both in metabolic syndrome and male infertility. Hypogonadism is also associated with increased risk for cardiovascular disease. To investigate the role of gonadal steroids in systemic antioxidant regulation, we determined plasma CoenzymeQ₁₀ (CoQ₁₀) and total antioxidant capacity (TAC) in postsurgical hypopituitaric patients. Twenty-six patients aged 28–55 years were studied 6–12 months after surgery. CoQ₁₀ levels were measured by high-performance liquid chromatography and TAC by spectroscopy with the use of the mioglobin-H₂O₂ system, which, in interacting with chromogen 2,2^I-azinobis-(3-ethylbenzothiazoline-6-sulfonate), generates a radical after a latency time (LAG) that is proportional to antioxidant content. Sixteen patients presented low testosterone values; in 10 patients hypogonadism was isolated, and in 6 patients hypothyroidism also was present. CoQ₁₀ levels were significantly lower in isolated hypogonadism than in normogonadism. Testosterone treatment, performed in those patients with isolated hypogonadism, induced a significant enhancement both in CoQ₁₀ level and LAG. CoQ₁₀ and LAG values correlated significantly, suggesting an interrelationship between different antioxidants. Our data suggest that hypogonadism could represent a condition of oxidative stress, in turn related with augmented cardiovascular risk.

     Key words: Androgen, oxidative stress, coenzyme Q₁₀, total antioxidant capacity

Oxidative stress from an imbalance between reactive oxygen species (ROS) and antioxidant defense, can underlie both these phenomena. However, the role of gonadal steroids in the regulation of systemic antioxidants is not known.

It has already been recognized that seminal total antioxidant capacity (TAC), which reflects nonenzymatic antioxidants, significantly correlates with follicle-stimulating hormone (FSH), luteinizing hormone (LH), and free T3 (fT3), but not with testosterone (Mancini et al, 2005,Mancini et al, 2005). In previous works, we have demonstrated alterations of plasma coenzyme Q₁₀ (CoQ₁₀), a lipidic antioxidant also endowed with bioenergetic properties, in pituitary diseases such as acromegaly or secondary hypothyroidism. In particular, in patients with acromegaly, the plasmatic value of CoQ₁₀ was low; in hypothyroidism CoQ₁₀ levels were higher than controls, showing a significant inverse correlation with thyroidal hormones fT3 and free T4 (fT4) (Mancini et al, 1989, 1991, 1992).

Finally, a relationship between sex hormones and plasmatic TAC was already observed (Demirbag et al, 2005). In fact, estradiol correlated with TAC, showing lower levels in postmenopausal than in premenopausal women. Similarly, in men, testosterone correlated with TAC, being lower in hypogonadal than in normogonadal men. The exact molecular mechanism of this action is not known, but estrogens are potent antioxidants both in vitro and in vivo (Avres et al, 1996), especially in terms of protection of fatty acid peroxidation. Both testosterone and estradiol were shown to increase the effects of antioxidant enzymes such as glutathione peroxidase (Massafra et al, 2000). In vivo, significant cycle phase–related changes in this enzyme were observed in cycling women with positive correlation between estradiol and erythrocyte glutathione-peroxidase (Massafra et al, 1998).

To investigate the role of gonadal steroids in the regulation of systemic antioxidants, we determined blood plasma CoQ₁₀ and TAC in a group of hypopituitaric patients after transsphenoidal removal of nonsecreting pituitary adenomas or craniopharyngiomas. The first objective was to compare hypogonadal patients to normogonadal ones. However, because of the complexity of this postoperative model and the involvement of different pituitary-dependent axes and to explain the confounding effect of hypothyroidism on antioxidants, patients with hypothyroidism and hypogonadism were compared with patients with isolated hypogonadism. Finally, the effect of testosterone replacement therapy was evaluated in patients with isolated hypogonadism.

	Subjects, Materials, and Methods

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Twenty-six male subjects aged 28–55 years entered this study after giving informed consent. The study was conducted in accordance with the guidelines in the Declaration of Helsinki. The patients were studied at 6–12 months after neurosurgical operation via transsphenoidal route to remove a nonsecreting pituitary adenoma or craniopharyngioma. All patients were hypopituitaric, with replacement therapy for thyroidal (ranging from 50 to 100 µg of L-thyroxine daily according to body weight) and adrenal (20–30 mg of hydrocortisone daily) axes. Patients were classified as normo- or hypogonadal according to their testosterone levels; no androgen replacement therapy had been previously performed before the study. Exclusion criteria for our study included diseases with well-known decreased levels of CoQ₁₀: cardiac, metabolic, cerebral, neuromuscular and mitochondrial diseases (Beal and Russel, 1997; Koroshetz et al, 1997; Thomas et al, 2001; Singh and Narankar, 2003; Yalcin et al, 2004). In the second step, when comparing data before and after androgen therapy, a further added exclusion criterion was the persistence of abnormal thyroid hormones values, because of the demonstrated predominant confounding effect of both hypo- and hyperthyroidism (Mancini et al, 1991).

A blood sample was collected at 0800 hours, for the determination of testosterone (T), estradiol (E2), dihydrotestosterone (DHT), sex hormone–binding globulin (SHBG), luteinizing hormone (LH), follicle-stimulating hormone (FSH), free T3 (fT3), free T4 (fT4), thyroid-stimulating hormone (TSH), prolactin (PRL), insulin-like growth factor 1 (IGF-1), CoQ₁₀, total cholesterol levels, and TAC in blood plasma. After centrifugation at 2000 x g for 10 minutes, plasma aliquots were immediately stored at –80°C, until assayed. Finally, urinary cortisol (F_U) was assayed in a sample from a 24-hour collection.

Moreover, patients with isolated hypogonadism were also studied after a 6-month treatment with testosterone enantate (250 mg IM every 3 weeks). Blood collection in the testosterone-treated group was performed on the seventh day after the last testosterone enantate injection, according to the kinetic profile of the drug.

Testosterone, estradiol, prolactin, and thyroid hormones were assayed in duplicate by radioimmunoassay (RIA) with the use of commercial kits by Radim (Pomezia, Italy). LH, FSH, and SHBG were assayed by immunoradiometric methods on a solid-phase (coated tube), which is based on a monoclonal double-antibody technique. Dihydrotestosterone and urinary cortisol were assayed by RIA with the use of commercial kits by Chematil (Angri, Italy). Plasma IGF-1 was measured by the immunoradiometric assay method with the use of kits from Medgenix Diagnostix SA (Fleurus, Belgium); soluble IGF-1 was separated from interfering binding proteins by the acid-ethanol procedure of Daughaday (1980). Free testosterone (free T) was calculated according to the formula proposed by Vermeulen et al (1999).

Reference values of the studied hormones were: T 12.14–34.67 nmol/L; free T 174–902 pmol/L; E2 36.7–128.45 pmol/L; DHT 1.04–2.94 nmol/L; SHBG 15–65 nmol/L; LH 2.5–10 IU/L; FSH 2.5–11 IU/L; fT3 3.54–6.46 pmol/L; fT4 10.93–19.94 pmol/L; TSH 0.35–2.80 mIU/L; PRL 3.5–15.5 µg/mL; F_U 99.3–377.9 nmol/d; and IGF-1, 80–330 µg/L. The intra-assay coefficients of variation (CV, %) were 6.1% for T, 2.3% for E2, 5.1% for DHT, 6.9% for SHBG, 5.6% for LH, 6.9% for FSH, 4.5% for TSH, 4.1% for fT4, 3.8% for fT3, 2.1% for PRL, 5.3% for F_u, 4.1% for IGF-1. The interassay coefficients of variation were 9.3% for T, 3.5% for E2, 8.9% for DHT, 8.5% for SHBG, 9.1% for LH, 8.4% for FSH, 3.4% for TSH, 4.9% for fT4, 3.9% for fT3, 3.1% for PRL, 8.9% for F_U, and 9.6% for IGF-1.

CoQ₁₀ levels were measured by a well-recognized high-performance liquid chromatography (HPLC) method (Mosca et al, 2002). The method is based on oxidation of CoQ₁₀ in the sample by treating it with para-benzoquinone followed by extraction with 1-propanol and direct injection into the HPLC apparatus. Preoxidation of the sample ensures quantification of total CoQ₁₀ by ultraviolet (UV) detection. This method achieves a linear detector response for peak area measurements over the concentration range of 0.05–3.47 µM. Diode array analysis of the peak was consistent with CoQ₁₀ spectrum. Supplementation of the samples with known amounts of CoQ₁₀ yielded a quantitative recovery of 96%–98.5%. The method showed a level of quantitation of 1.23 nmol per HPLC injection (200 µL of propanol extract containing 33.3 µL of plasma). A good correlation was found with a reference electrochemical detection method (r = 0.99, P < 0.0001). Within-run precision showed a CV of 1.6% for samples approaching normal values (1.02 µM). Day-to-day precision was also close to 2%. Reference values of CoQ₁₀ are 810.74–1158.20 nmol/L (Tomasetti et al, 1999). Moreover, CoQ₁₀ values were related to plasma cholesterol concentration, measured by a cholesterol-oxidase enzymatic test.

Total antioxidant capacity (TAC) was evaluated as previously described (Meucci et al, 2003), with a modification of the method developed by Rice-Evans and Miller (1994). The method is based on antioxidant inhibition of the absorbance of the radical cation 2,2^I-azinobis (3-ethyl-benzothiazoline-6 sulfonate) (ABTS^•+) formed by interaction between ABTS (150 µM) and ferrylmyoglobin radical species generated by activation of metmyoglobin (2.5 µM) with H₂O₂ (75 µM). Aliquots of the frozen plasma were thawed at room temperature, and 10 µL of the samples was tested immediately. The manual procedure was used with only minor modifications (ie, temperature was set at 37°C to be in more physiological conditions) and each sample was assayed alone to carefully control timing and temperature. The reaction was started directly in a cuvette through H₂O₂ addition after 1 minute of equilibration of all other reagents (temperature controlled by a thermocouple probe, model 1408 K thermocouple, Digitron Instrumentation Ltd, Scunthorpe, United Kingdom) and followed for 10 minutes under continuous stirring, with monitoring at 734 nm, as is typical for spectroscopically detectable ABTS^•+. The presence of chain-breaking antioxidants induces a lag time (the LAG phase) in the accumulation of ABTS^•+, whose length (s) is proportional to the concentration of these types of antioxidants. In the LAG mode, the assay mainly measures nonprotein and nonenzymatic antioxidants that are primarily extracellular chain-breaking antioxidants, such as ascorbate, urate, and glutathione (Meucci et al, 2003). Trolox, a water-soluble tocopherol analog, was used as a reference standard and assayed in all experiments to control the system. Absorbance was measured with a Hewlett-Packard 8450A UV/visible (UV/Vis) spectrophotometer (Palo Alto, California) equipped with a cuvette stirring apparatus and a constant temperature cell holder. Measurements of pH were made with a PHM84 Research pH meter (Radiometer, Copenhagen, Denmark); the electrode response was corrected for temperature. Unless stated differently, experiments were repeated 2 to 3 times; intra- and interassay coefficients of variation were less than 8%.

Distribution of data was estimated by the Kolmogorov-Smirnov test. Because data were not normally distributed, comparison among groups was made with the Mann-Whitney U test, and comparison between the same patients, before and after therapy, was performed by the Wilcoxon rank sum test. Linear correlation analysis was also employed. Arcus Quickstat (Software Publishing Biomedical version 1.2, Cambridge, United Kingdom) was used for the statistical analysis.

	Results

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Sixteen of the 26 hypopituitaric patients presented low levels of testosterone, which were normal in the remaining 10 patients. CoQ₁₀ and LAG were lower, although not significantly, in hypogonadal than in normogonadal patients (see Table 1).

View this table: [in this window] [in a new window]   Table 1. Hormone and antioxidant levels ( ± SEM) in patients classified into 2 groups according to testosterone level

The 16 hypogonadal patients also needed replacement therapy for secondary thyroidal and adrenal deficiencies; normal IGf-1 values indicated preservation of the GH-IGf-1 axis. Despite thyroid replacement therapy, at the time of the study, only 10 hypogonadal patients exhibited normalization of thyroid values, whereas 6 hypogonadal patients remained hypothyroidal (see Table 2); all the patients showed normal cortisol levels under replacement therapy. When we divided hypogonadal patients in normo- and hypothyroidal, we found a significantly lower CoQ₁₀ value in isolated hypogonadism (see Table 2); CoQ₁₀ in isolated hypogonadism was also significantly lower than in normogonadal subjects (P < .05). When the concentrations of CoQ₁₀ were normalized to cholesterol values, the trend was the same, but the differences among the groups were not significant (see Table 2).

View this table: [in this window] [in a new window]   Table 2. Hormone and antioxidant levels ( ± SEM) in patients with hypogonadism classified into 2 subgroups according to thyroid hormone levels

CoQ₁₀ and CoQ₁₀/cholesterol significantly correlated with LAG values (r = 0.5, P < .005 and r = 0.7, P < .001, respectively), suggesting an interrelationship between different antioxidants in the whole group of patients (see Figure 1).

View larger version (18K): [in this window] [in a new window]   Figure 1. Scattered plotting of linear correlation analysis between (A) CoQ10 values or (B) CoQ10/cholesterol ratio and LAG. r indicates Spearman's coefficient.

View larger version (31K): [in this window] [in a new window]   Figure 2. Levels of testosterone ( ± SEM), CoQ10, CoQ10/cholesterol, and LAG in patients with isolated hypogonadism before and after testosterone treatment. * P < .05 compared with pretreatment values.

	Discussion

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Epidemiological observations suggest a relationship between hypogonadism and cardiovascular diseases. Recent studies have shown that men with coronary artery disease (CAD) have significantly lower concentrations of bioavailable testosterone than men with normal angiograms (English et al, 2000). The prevalence of hypogonadism in a population of men with CAD is about twice that observed in the general population (Morris et al, unpublished data). Hypotestosteronemia is associated with an atherogenic lipid profile (elevated low-density lipoproteins and triglycerides, decreased high-density lipoprotein), high fibrinogen with a hypercoagulable state, an increase in insulin resistance and hyperinsulinemia, and higher systolic and diastolic blood pressure (English et al, 1997).

Experimental data also reinforce the concept of a positive effect of exogenous testosterone administration. In an animal model, castration increased aortic atheroma formation, and testosterone replacement ameliorated this effect (Alexandersen et al, 1999). In addition, testosterone has direct vasoactive properties, which directly affect the vascular smooth muscle, not mediated by the nuclear androgen receptor, in that the effect is too rapid and is not reduced by flutamide, a nuclear androgen receptor blocker (Deenadayalu et al, 2001; English et al, 2001, 2002). When testosterone is instilled into the left coronary artery, vasodilatation ensues and coronary flow increases (Webb et al, 1999b). More importantly, acute administration of intravenous testosterone improves exercise tolerance and reduces the angina threshold in men with CAD (Rosano et al, 1999; Webb et al, 1999a). These positive effects seem to be related to the nongenomic action of testosterone on vascular smooth muscle cells (Jones et al, 2003a,b).

Oxidative stress can underlie the above-mentioned clinical conditions. As demonstrated by statistical meta-analysis, low testosteronemia and androgen deficiency were associated with an increased risk of developing a metabolic syndrome over time (Kupelian et al, 2006). However, the pathophysiological details of these changes in atherosclerosis (Von Eckardstein and Wu, 2004) and implications in testosterone replacement therapy (Nieschlag et al, 2004) are still under investigation. Moreover, the role of gonadal steroids in the regulation of systemic antioxidants is not known. We therefore investigated the role of CoQ₁₀, a lipidic antioxidant, and the TAC of blood plasma in secondary male hypogonadism.

Coenzyme Q₁₀ is well defined as a crucial component of the oxidative phosphorylation process in mitochondria. It can undergo oxidation/reduction reactions in other cell membranes such as lysosomes and Golgi or plasma membranes. The presence of high concentrations of quinol in all membranes provides a basis for antioxidant action, either by direct reaction with radicals or by regeneration of tocopherol and ascorbate (Crane and Frederick, 2001). Evidence for a function in redox control of cell signaling and gene expression can be found in studies on CoQ stimulation of cell growth, inhibition of apoptosis, control of thiol groups, formation of hydrogen peroxide, and control of membrane channels (Groneberg et al, 2005). Thyroid hormones exert a profound influence on CoQ₁₀, as previously demonstrated (Mancini et al, 1991). Hyperthyroid patients exhibit extremely low CoQ₁₀ levels. The possible mechanisms include: 1) decreased synthesis, related to the competition for tyrosine, which is a common substrate for CoQ and thyroxine synthesis (Olson, 1983), even if this hypothesis is disconfirmed by experimental data in animals (Ikeda et al, 1984; Horrum et al, 1986); 2) increased CoQ₁₀ utilization through the increased stimulation of energy metabolism; 3) increased degradation; 4) decreased levels of carriers in serum, in that it has been demonstrated that the very low density lipoprotein release from liver is decreased in hyperthyroid states (Keyes et al, 1981). The opposite mechanisms could explain higher CoQ₁₀ levels in hypothyroidism.

Another important parameter of the body's antioxidant defense is plasmatic TAC, which is studied with greater frequency. Representing the functional sum of antioxidants present in plasma, it is a measure of the extracellular antioxidant barrier (Prior and Cao, 1999; Chevion and Chevion, 2000; Bartoz, 2003). In a recent work, TAC was determined during cardiovascular bypass surgery in patients with coronary heart disease: TAC decreased during surgery, but no further decrease in TAC was observed during reperfusion, indicating that it is a relatively stable parameter of the antioxidant barrier of the body (Kedziora-Kornatowska et al, 2003). Finally, a relationship between sex hormones and plasmatic TAC had already been observed (Demirbag et al, 2005). For this study, we measured TAC by a novel automated method (Erel, 2004). TAC (as mmol Trolox equivalent/L) significantly correlated with total testosterone in male subjects and also with estradiol in a group of pre- and postmenopausal women (Demirbag et al, 2005). No effect of androgens was observed on erythrocyte antioxidant systems in cycling women (Massafra et al, 2000).

Conflicting results do not allow unequivocal conclusions on the role of androgens in coronary artery disease in recent reviews (Liu et al, 2003; Wu and von Eckardstein, 2003). Many confounding factors contribute to making this question very complex. Studies on endogenous androgen levels depend on different mechanisms, such as gender-specific gene expression, distribution of body fat, vascular factors, and adaptation to aging. Similarly, studies on exogenous androgen administration are influenced by dose, route of administration, duration of treatment, and again gender, age, and condition of recipients. Moreover, the androgen effects—genomic and nongenomic, aromatization-mediated or not, anti- and pro-atherogenic mechanisms—on the cardiovascular system is growing rapidly, but it still does not allow a conclusive picture. Therefore, data on antioxidant regulation by steroids can be useful to clarify molecular mechanisms of testosterone action.

Even though the relationship between systemic and seminal antioxidants and the systemic regulation of seminal antioxidants are still poorly understood, our data suggest that CoQ₁₀ levels are significantly lower in secondary isolated hypogonadal compared with normogonadal patients with the same physiopathological postoperative condition. However, because thyroid hormones have an important role in modulating CoQ₁₀ levels and metabolism (Mancini et al, 1991), when coexistent, thyroid deficiency could be more important in influencing antioxidant levels than hypogonadism. Other explanations such as thyroid influence on gonadal hormones are unlikely in this particular clinical model. It is well known that hypothyroidism per se reduces the clearance of testosterone and increases SHBG (Larsen and Davies, 2003), but these mechanisms are not relevant in our model in which both axes are depressed because of the pituitary surgery. The same consideration concerns the possible effects of hypothyroidism on GnRH secretion (Toni et al, 2005) and on Leydig cell steroidogenesis (Mendis-Handagama and Siril Ariyaratne, 2005). The influence of the pituitary-adrenal axis and of growth hormone, which can affect antioxidant levels (Brown-Borg et al, 1999; Mancini et al, 2005,Mancini et al, 2005) were excluded on the basis of normal cortisol and IGF-1 levels.

Testosterone therapy reported values toward the same levels observed in normogonadic patients, with a significant increase in CoQ₁₀ concentrations. TAC, expressed as LAG, which exhibited a trend toward lower values in hypogonadal subjects, also increased significantly with testosterone treatment.

Our data reinforce the concept that hypogonadism could represent a condition of oxidative stress. Although the small number of patients studied does not allow definitive conclusions, lower levels of CoQ₁₀ were discovered in isolated hypogonadal compared with normogonadal patients. To our knowledge, this is the first report of the testosterone effect on antioxidant systems in humans. Further studies can clarify the relationship of this datum with the augmented cardiovascular risk in such patients.

	References

Top Abstract Subjects, Materials, and Methods Results Discussion References

 
Alexandersen P, Haarbo J, Byrjalsen I, Lawaetz H, Christiansen C. Natural androgens inhibit male atherosclerosis. A study of castrated, cholesterol fed rabbits. Circ Res. 1999; 84: 813 –819.[Abstract/Free Full Text]

Avres S, Tang M, Subbiah MT. Estradiol-17beta as an antioxidant: some distinct features when compared with common fat-soluble antioxidants. J Lab Clin Med. 1996; 128(4): 367 –375.[CrossRef][Medline]

Bartoz G. Total antioxidant capacity. Adv Clin Chem. 2003;37: 219 –292.[CrossRef][Medline]

Beal MF, Russel TM. Coenzyme Q₁₀ in the central nervous system and its potential usefulness in the treatment of neurodegenerative diseases. Mol Aspects Med. 1997; 18: 169 –179.[CrossRef]

Brown-Borg HM, Bode AM, Bartke A. Antioxidative mechanisms and plasma growth hormone levels: potential relationship in the aging process. Endocrine. 1999; 11(1): 41 –48.[CrossRef][Medline]

Channer KS, Jones TH. Cardiovascular effects of testosterone: implications of the "male menopause"? Heart. 2003;89: 121 –122.[Free Full Text]

Chevion S, Chevion M. Antioxidant status and human health. Use of cyclic voltammetry for the evaluation of the antioxidant capacity of plasma and of edible plants. Ann N Y Acad Sci. 2000; 899: 308 –325.[Medline]

Crane P, Frederick L. Biochemical functions of coenzyme Q10. J Am Coll Nutr. 2001; 20: 591 –598.[Abstract/Free Full Text]

Daughaday WH, Mariz IK, Blethen SL. Inhibition of access of bound somatomedin to membrane receptor and immunobinding sites: a comparison of radioreceptor and radioimmunoassay of somatomedin in native and acid-ethanol-extracted serum. J Clin Endocrinol Metab. 1980; 51: 781 –788.[Abstract/Free Full Text]

Deenadayalu VP, White RE, Stallone JN, Gao X, Garcia AJ. Testosterone relaxes coronary arteries by opening the large-conductance, calcium-activated potassium channel. Am J Physiol Heart Circ Physiol. 2001;281: 1720 –1727.

Demirbag R, Yilmaz R, Erel O. The association of total antioxidant capacity with sex hormones. Scand. Cardiovasc J. 2005; 39: 172 –176.[CrossRef][Medline]

English K, Steeds RP, Jones TH, Channer KS. Testosterone and ischaemic heart disease: is there a link? QJM. 1997; 90: 787 –791.[Free Full Text]

English KM, Jones RD, Jones TH, Morice AH, Channer KS. Gender differences in the vasomotor effects of different steroid hormones in rat pulmonary and coronary arteries. Horm Metab Res. 2001; 33: 645 –652.[CrossRef][Medline]

English KM, Jones RD, Jones TH, Morice AH, Channer KS. Testosterone acts as a coronary vasodilator by a calcium channel antagonist action. J Endocrinol Invest. 2002; 25: 455 –458.[Medline]

English KM, Mandour O, Steeds RP, Diver MJ, Jones TH, Channer KS. Men with coronary artery disease have lower levels of testosterone than those with normal coronary angiograms. Eur Heart J. 2000; 21: 890 –894.[Abstract/Free Full Text]

Erel O. A novel-automated method to measure total antioxidant response against potent free radical reactions. Clin Biochem. 2004;37: 112 –119.[CrossRef][Medline]

Groneberg DA, Kindermann S, Althammer M, Klapper M, Vormann J, Littarru GP, Doring F. Coenzyme Q₁₀ affects expression of genes involved in cell signalling, metabolism and transport in human CaCO-2 cells. Int J Biochem Cell Biol. 2005; 37: 1208 –1218.[CrossRef][Medline]

Haffner SM, Karhapää P, Mykkänem L, Laakso M. Insulin resistance, body fat distribution, and sex hormone in men. Diabetes. 1994a; 43: 212 –219.[Abstract]

Haffner SM, Valdez RA, Mykkanem L, Stern MP, Katz MS. Decreased testosterone and dehydroepiandrosterone sulphate concentrations are associated with increased insulin and glucose concentrations in non-diabetic men. Metabolism. 1994b; 43: 599 –603.[CrossRef][Medline]

Horrum MA, Tobin RB, Ecklund RE. Thyroxine-induced changes in rat liver mitochondrial ubiquinone. Biochem Biophys Res Commun. 1986; 138(1): 381 –386.[CrossRef][Medline]

Ikeda S, Hamada N, Morii H, Inaba M, Yamakawa J. Serum and tissue coenzyme Q9 in rats with thyroid dysfunctions. Horm Metab Res. 1984;16: 585 –588.[Medline]

Jones RD, Pugh PJ, Jones TH, Channer KS. The vaso-dilatory action of testosterone—a potassium channel opening or a calcium channel antagonistic action. Br J Pharmacol. 2003a; 138: 733 –744.[CrossRef][Medline]

Jones RD, Ruban LN, Morton IE, Roberts SA, English KM, Channer KS, Jones TH. Testosterone inhibits the prostaglandin F₂-mediated increase in intracellular calcium in A7r5 aortic smooth muscle cells: evidence of an antagonistic action upon store operated calcium channels. J Endocrinol. 2003b; 178: 381 –393.[Abstract]

Kedziora-Kornatowska K, Bartosz M, Mussur M, Zasonka J, Kedziora J, Bartosz G. The total antioxidant capacity of blood plasma during cardiovasculary bypass surgery in patients with coronary heart disease. Cell Mol Biol Lett. 2003; 8: 973 –977.[Medline]

Keyes WG, Wilcox HG, Heimberg M. Formation of the very low density lipoprotein and metabolism of [1-14C]-oleate by perfused livers from rats treated with triiodothyronine or propylthiouracil. Metabolism. 1981; 30: 135 –146.[CrossRef][Medline]

Koroshetz WJ, Jenkins BG, Rosen BR, Beal MF. Assessment of energy metabolism defects in Huntington's disease and possible therapy with coenzyme Q₁₀. Ann Neurol. 1997; 41: 160 –165.[CrossRef][Medline]

Kupelian V, Page ST, Araujo AB, Travison TG, Bremner WJ, McKinlay JB. Low sex hormone–binding globulin, total testosterone, and symptomatic androgen deficiency are associated with development of the metabolic syndrome in nonobese men. J Clin Endocrinol Metab. 2006;91: 843 –850.[Abstract/Free Full Text]

Larsen PR, Davies TF. Hypothyroidism and thyroiditis. In: Larsen PR, Kronenberg HM, Melmed S, Polonsky KS, eds. Williams Textbook of Endocrinology. 10th ed. Philadelphia: Saunders; 2003 : 423–455.

Liu PY, Death AK, Handelsman DJ. Androgens and cardiovascular disease. Endocr Rev. 2003; 24(3): 313 –340.[Abstract/Free Full Text]

Mancini A, Bianchi A, Fusco A, Sacco E, Leone E, Tilaro L, Porcelli T, Giampietro A, Principi F, De Marinis L, Littarru GP. Coenzyme Q10 evaluation in pituitary-adrenal axis disease: preliminary data. Biofactors. 2005; 25: 197 –199.[Medline]

Mancini A, Calabrò F, Fiumara C, Conte G, Oradei A, Lippa S, De Marinis L, Littarru GP. Plasma coenzyme Q10 determination in acromegaly. Exp Clin Endocrinol Life Sci Adv. 1992; 11: 55 –60.

Mancini A, De Marinis L, Calabrò F, Fiumara C, Goglia A, Sofo L, Lippa S, Oradei A, Rabitti C, Littarru GP. Physiopathological relevance of coenzyme Q10 in thyroid disorders: CoQ10 concentrations in normal and diseased human thyroid tissue. In: Folkers K, Littarru GP, Yamagami T, eds. Biomedical and Clinical Aspects of Coenzyme Q. Amsterdam: Elsevier; 1991: 441 –448.

Mancini A, De Marinis L, Calabrò F, Sciuto R, Oradei A, Lippa S, Sandric S, Littarru GP, Barbarino A. Evaluation of metabolic status in amiodarone-induced thyroid disorders: plasma coenzyme Q10 determination. J Endocrinol. Invest. 1989; 12: 511 –516.[Medline]

Mancini A, Milardi D, Bianchi A, Meucci E, Pontecorvi A, De Marinis L. Hormonal regulation of total antioxidant capacity in seminal plasma. In: Kim S, Grootegoed JA, Chemes HE, eds. Proceedings of the 8th International Congress of Andrology. Seoul, Korea, Free Papers. Bologna: Medimond; 2005: 59 –62.

Massafra C, De Felice C, Gioia D, Buonocore G. Variations in erythrocyte antioxidant glutathione peroxidase activity during the menstrual cycle. Clin Endocrinol. 1998; 49: 63 –67.[CrossRef][Medline]

Massafra C, Gioia D, De Felice C, Picciolini E, De Leo V, Bonifazi M, Bernabei A. Effects of estrogens and androgens on erythrocyte antioxidant superoxide dismutase, catalase and glutathione peroxidase activities during the menstrual cycle. J Endocrinol. 2000; 167: 447 –452.[Abstract]

Mendis-Handagama SM, Siril Ariyaratne HB. Leydig cells, thyroid hormones and steroidogenesis. Indian J Exp Biol. 2005; 43(11): 939 –962.[Medline]

Meucci E, Milardi D, Mordente A, Martorana GE, Giacchi E, De Marinis L, Mancini A. Total antioxidant capacity in patients with varicoceles. Fertil Steril. 2003; 79(3): 1577 –1583.[CrossRef][Medline]

Mosca F, Fattorini D, Bompadre S, Littarru GP. Assay of coenzyme Q(10) in plasma by a single dilution step. Anal Biochem. 2002;305: 49 –54.[CrossRef][Medline]

Nieschlag E, Behre HM, Bouchard P, Corrales JJ, Jones TH, Stalla GK, Webb SM, Wu FCW. Testosterone replacement therapy: current trends and future directions. Hum Reprod. 2004; 10: 409 –419.

Olson RE, Rudney H. Biosynthesis of ubiquinone. Vitam Horm. 1983;40: 1 –43.[Medline]

Prior RL, Cao G. In vivo total antioxidant capacity: comparison of different analytical methods. Free Radic Biol Med. 1999; 27: 1173 –1181.[CrossRef][Medline]

Rice-Evans C, Miller NJ. Total antioxidant status in plasma and body fluids. Methods Enzymol. 1994; 234: 279 –293.[Medline]

Rosano GMC, Leonardo F, Pagnotta P, Pelliccia F, Panina G, Cerquetani E, Della Monica PL, Bonfigli B, Volpe M, Chierchia SL. Acute anti-ischaemic effect of testosterone in men with coronary artery disease. Circulation. 1999; 99: 1666 –1670.[Abstract/Free Full Text]

Simon D, Preziosi P, Barrett-Connor E, Roger M, Saint-Paul M, Nahoul K, Papoz L. Interrelation between plasma testosterone and plasma insulin in healthy adult men: the Telecom study. Diabetologia. 1992; 35: 173 –177.[CrossRef][Medline]

Singh RB, Narankar SF. Effect of coenzyme Q₁₀ on risk of atherosclerosis in patients with recent myocardial infarction. Mol Cell Biochem. 2003;246: 75 –82.[CrossRef][Medline]

Thomas ST, Leichtweis SB, Pettersson K, Croft K. Dietary cosupplementation with vitamin E and CoQ₁₀ inhibits atherosclerosis in apolipoprotein E gene knockout mice. Arterioscler Thromb Vasc Biol. 2001;21: 585 –593.[Abstract/Free Full Text]

Tomasetti M, Alleva R, Solenghi MD, Littarru GP. Distribution of antioxidants among blood components and lipoproteins: significance of lipids/CoQ₁₀ ratio as a possible marker of increased risk for atherosclerosis. Biofactors. 1999; 9: 231 –240.[Medline]

Toni R, Della Casa C, Castorina S, Cocchi D, Celotti F. Effects of hypothyroidism and endocrine disruptor–dependent non-thyroidal illness syndrome on the GnRH-gonadotroph axis of the adult male rat. J Endocrinol Invest. 2005; 28(11 suppl proc): 20 –27.[Medline]

Vermeulen A, Rubens R, Verdonck L. Testosterone secretion and metabolism in male senescence. J Clin Endocrinol Metab. 1972;34: 730 –735.[Abstract/Free Full Text]

Vermeulen A, Verdonck L, Kaufman JM. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab. 1999; 84: 3666 –3672.[Abstract/Free Full Text]

Von Eckardstein A, Wu FCW. Testosterone and cardiovascular disease. In: Nieschlag E, Behre HM, eds. Testosterone: Action, Deficiency, Substitution. 3rd ed. Cambridge: University Press; 2004 : 297–331.

Webb CM, Adamson DL, de Zeigler D, Collins P. Effect of acute testosterone on myocardial ischaemia in men with coronary artery disease. Am J Cardiol. 1999a; 83: 437 –439.[CrossRef][Medline]

Webb CM, McNeill JG, Hayward CS, De Zeigler D, Collins P. Effects of testosterone on coronary vasomotor regulation in men with coronary heart disease. Circulation. 1999b; 100: 1690 –1696.[Abstract/Free Full Text]

Wu FCW, von Eckardstein A. Androgens and coronary artery disease. Endocr Rev. 2003; 24(2): 183 –217.[Abstract/Free Full Text]

Yalcin A, Kilinc E, Sagcan A, Kultursay H. Coenzyme Q₁₀ concentrations in coronary artery disease. Clin Biochem. 2004;37: 706 –709.[CrossRef][Medline]

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