Effect of fluoxymesterone on the pituitary-gonadal axis: the role of testosterone-estradiol-binding globulin

Biochemical and physiological aspects of endogenous androgens

This review attempts to give a synopsis of the major aspects concerning the biochemistry of endogenous androgens, supplemented with several facets of physiology, particularly with respect to testosterone. Testosterone continues to be the most common adverse finding declared by World Anti-Doping Agency accredited laboratories, such samples having an augmented testosterone to epitestosterone ratio. Knowledge regarding the precursors and metabolism of endogenous testosterone is therefore fundamental to understanding many of the issues concerning doping with testosterone and its prohormones, including the detection of their administration. Further, adverse findings for nandrolone are frequent, but this steroid and 19-norandrostenedione are also produced endogenously, an appealing hypothesis being that they are minor by-products of the aromatization of androgens. At sports tribunals pertaining to adverse analytical findings of natural androgen administration, experts often raise issues that concern some aspect of steroid biochemistry and physiology. Salient topics included within this review are the origins and interconversion of endogenous androgens, the biosynthesis of testosterone and epitestosterone, the mechanism of aromatization, the molecular biology of the androgen receptor, the hypothalamic-pituitary-testicular axis, disturbances to this axis by anabolic steroid administration, the transport (binding) of androgens in blood, and briefly the metabolism and excretion of androgens.

Testosterone's short-term positive effect on luteinizing-hormone secretory-burst mass and its negative effect on secretory-burst frequency are attenuated in middle-aged men

BACKGROUND

Testosterone (T) production declines and LH pulses become smaller and more frequent in middle-aged men. The mechanisms underlying these changes are not known.

RATIONALE

Small frequent LH pulses in middle-aged men could reflect impaired feedback by systemic T.

HYPOTHESIS

Middle age disrupts negative feedback by T on selected facets of LH secretion.

SUBJECTS AND SETTING

Healthy men were studied at an academic medical center.

METHODS

The protocol comprised blockade of gonadal steroidogenesis and graded transdermal addback of T doses of 0, 2.5, 5, or 7.5 mg/d designed to span the castrate to physiological range of T concentrations in each of 23 healthy men ages 19-71 yr (interquartile range, 28-53 yr). We quantified 12-h basal and pulsatile LH secretion (92 time series) using a mathematically justified deconvolution method.

RESULTS

Stepwise T supplementation from the hypogonadal through the eugonadal range repressed mean (12-h) LH concentrations (P = 0.001). By regression analysis, age attenuated the capabilities of increasing T concentrations to 1) increase LH secretory-burst mass (P < 0.0001); and 2) decrease LH secretory-burst frequency (P = 0.025). Age did not alter T's feedback on basal LH secretion, interpulse regularity, the waveform of LH secretory bursts, or the slow half-life of LH.

CONCLUSION

Middle age impairs both the positive and negative actions of systemic T on pulsatile LH secretion in healthy men, thus potentially explaining earlier inconsistencies in feedback studies based upon single-sample mean LH concentrations. Longitudinal studies will be required to elucidate the precise age dependence of inferred dual feedback failure.

Impact level of dihydrotestosterone on the hypothalamic-pituitary-leydig cell axis in men

Dihydrotestosterone (DHT) the physiologically most potent androgen cannot be aromatised into oestrogen. DHT is used as a treatment for idiopathic gynaecomastia. In order to investigate the different sites of action of DHT on the hypothalamic-pituitary-testicular axis, two groups of adult men were studied. Group I included 10 gonadotropin-releasing hormone (GnRH)-deficient men who were evaluated before and during a pulsatile infusion of GnRH alone for 2 weeks and then in association with DHT given transdermally at doses used in the treatment of gynaecomastia for further two weeks. Luteinizing hormone (LH) pulsatility was assessed at the end of each step of the study. Plasma LH levels were measured every 15 min. Plasma testosterone (T), DHT, oestradiol (E2), free alpha-subunit (FAS) of glycoproteic hormones and LH bioactivity were measured on pooled plasma samples. Group II included 12 healthy men in whom plasma T, DHT and E2 were measured before and then 24, 48 and 72 h after the injection of 5000 IU hCG alone or in combination with either DHT or the pure anti-androgen nilutamide. Two weeks separated each of the 3 hCG testing. In group I, except for bioactive/immunoreactive (B/I) LH ratio which was unchanged, GnRH treatment induced significant rises (p < 0.01) in all plasma hormone levels, LH pulse amplitude and frequency. During treatment with GnRH+DHT, plasma DHT levels increased up to 16.8 +/- 2.5 nm, while plasma hormone levels, B/I LH ratio, LH pulse amplitude and frequency were similar to those obtained with GnRH alone. In group II, the peak of hCG-induced T rise was not modified by either DHT or nilutamide. In contrast, DHT reduced by 50% (p < 0.01) the E2 peak in response to hCG. These data show that DHT exerts no direct action on the pituitary to retroregulate LH secretion and to modify either B/I LH ratio or FAS secretion. Its reducing effect on LH secretion is likely mediated at the hypothalamic level. DHT does not appear to have a physiological influence on Leydig cells steroidogenesis. Administered at therapeutic doses, DHT directly reduces testicular aromatase activity that combined with its antigonadotropic effect leads to the gain in the symptomatic treatment of gynaecomastia.

Recent neuroendocrine facets of male reproductive aging

We recently identified consistent attenuation of LH and testosterone secretory pulse amplitude and associated disruption of their orderly patterns of release in healthy older men. These dynamic changes emerge despite young-adult concentrations of LH and total testosterone. Moreover, we could document disruption of synchrony between LH secretion and oscillations in FSH, prolactin, sleep-stage and NPT (nocturnal penile tumescence), thus pointing to loss of coordinate neurohormone outflow. Such data suggest that CNS-hypothalamically based regulatory defects may be important in aging, as inferred indirectly in the old male rat and mouse more than 15 years ago. How such alterations are related to specific hypothalamic neurotransmitter changes in aging will be critical to unravel.

Neuronal hypertrophy in the hypothalamus of older men

A striking neuronal hypertrophy occurs in the infundibular nucleus of postmenopausal women. To determine the gender specificity of this response, we measured the areas of neuronal profiles in the infundibular nucleus of young (21, 32, and 41 years) and older (60, 61, and 68 years) men and compared them to data reported previously from the hypothalami of pre-(28, 32, and 40 years) and postmenopausal women (58, 62, and 74 years). Sagittal blocks of formalin-fixed hypothalami were paraffin embedded, serially sectioned and stained with cresyl-violet. The profile areas of 2,429 infundibular neurons were manually digitized using an image-combining computer microscope. The contralateral hypothalamus of each subject was cryoprotected, frozen-sectioned in the coronal plane and also stained with cresyl violet. The infundibular nuclear volume and the total number of neurons were estimated from the coronal sections using stereological methods. The mean profile area of infundibular neurons from older men (176.6 +/- 1.7 microns 2) was significantly larger than that of young men (147.0 +/- 1.3 microns 2). There was also a significant increase in the density of hypertrophied neurons (> 226 microns 2 profile area) in the infundibular nucleus of older men. There was no difference in infundibular nucleus associated with an average neurons was significantly increased in the older men. A comparison with previous data obtained from pre- and postmenopausal women revealed that the profile area of infundibular neurons was equal in young men and young women. However, the profile area of neurons in the postmenopausal women (190.4 +/- 2.1 microns 2) was significantly greater than that of older men.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of oxandrolone on the growth hormone and gonadal axes in boys with constitutional delay of growth and puberty

OBJECTIVE

We studied the effects of oxandrolone on serum concentrations of LH, FSH, testosterone, GH, SHBG, DHEAS, IGF-I and insulin in boys with constitutional delay of growth and puberty.

DESIGN

Ten boys with constitutional delay of growth and puberty, mean age 13.8 years (range 12.4-15.5) were studied. Twenty-four-hour serum concentration profiles of GH, LH and FSH were constructed by drawing blood samples at 20-minute intervals. Three study occasions over a period of 6 months were chosen to assess hormone concentrations before, during and 6 weeks after a 3-month course of oxandrolone (2.5 mg once daily) therapy.

RESULTS

Growth velocity increased during oxandrolone treatment and stayed higher after therapy (pre 3.9 +/- 0.5; on 6.3 +/- 0.8; post 6.4 +/- 0.9 cm/year (mean +/- SEM) two way ANOVA, F = 5.3, P = 0.02). Oxandrolone had androgenic effects, suppressing mean serum LH concentrations from 1.7 +/- 0.3 to 1.1 +/- 0.2 U/I and serum testosterone concentrations from 1.9 +/- 0.6 to 0.8 +/- 0.1 nmol/l. SHBG concentrations were also reduced from 130.9 +/- 14.6 to 30.7 +/- 7.3 nmol/l. Serum GH concentration fell slightly from 5.9 +/- 0.6 to 4.8 +/- 0.5 mU/l. After cessation of treatment, there was a significant 'rebound' in mean 24-hour serum LH (2.6 U/l +/- 0.4) and testosterone concentrations (3.2 +/- 0.9 nmol/l) but no change in serum GH concentrations. SHBG values also rose but not to the same extent as those observed before therapy (82.0 +/- 8.4 nmol/l). There were no statistically significant differences in serum concentrations of FSH, DHEAS, IGF-I and insulin over the study period. In a stepwise multiple regression analysis of factors that might influence the growth rate observed, the 24-hour mean serum testosterone concentration and the treatment (on or off) with oxandrolone were the main influences. The relationship was described by the equation Height velocity = 0.69 (24-hour mean serum testosterone concentration)+1.70 (treatment regimen)+3.37 (adjusted R2 = 0.35, F = 8.39, P = 0.001).

CONCLUSIONS

Oxandrolone has an androgenic action as shown by changes in serum LH, testosterone and SHBG concentrations and by the lack of effect on FSH. No effect of oxandrolone on the GH axis was documented. We suggest that the growth promoting effects of oxandrolone are related in part to the mild androgenic effects of the steroid and the growth acceleration following oxandrolone withdrawal may reflect increasing total serum testosterone concentrations and decreasing levels of SHBG and progress in puberty.

The efficacy of ergogenic agents in athletic competition. Part I: Androgenic-anabolic steroids

OBJECTIVE

To summarize the literature describing the epidemiology, pharmacology, efficacy, and adverse effects associated with androgenic-anabolic steroid (AAS) use among athletes.

DATA SOURCES

Relevant articles were identified from a MEDLINE search using the search terms "Doping in Sports," "Anabolic Steroids (exploded)," and "Androgens (exploded)." Additional references were found in the bibliographies of these articles.

STUDY SELECTION/DATA EXTRACTION

We reviewed studies of AAS use among professional athletes. Interpretation of these studies is difficult because of poor research design. The efficacy studies lacked adequate placebo control. Much of the literature describing adverse effects consists of anecdotal reports. All of this literature was considered for review.

DATA SYNTHESIS

Of all ergogenic drugs, AASs are the most widely abused. Abuse of AASs among high school students is estimated at five to ten percent. AASs are hypothesized to produce ergogenic effects during periods of concomitant positive nitrogen balance via antagonism of the catabolic effect of glucocorticoids released during intense exercise. Despite years of study, the extent of the ergogenic effects associated with AASs remains unclear. This may be because most studies have failed to approximate athletes' AAS usage patterns. The primary toxic effects of AASs are divided into four areas: hepatic, reproductive, cardiovascular, and psychiatric. Athletes do not consider these effects severe enough to refrain from using these drugs.

CONCLUSIONS

Athletes view AASs as an essential component for success. Without adequate intervention measures, AAS abuse is likely to continue unchecked.

Serum high density lipoprotein subclasses, testosterone and sex-hormone-binding globulin in Trinidadian men of African and Indian descent

Serum high-density lipoprotein (HDL) cholesterol, testosterone and sex-hormone-binding globulin (SHBG) were measured in 300 men, aged 35-64 years, of African and Indian descent who represented a 40% sample of participants in a community survey of coronary heart disease in Trinidad. Free testosterone was calculated from total testosterone and SHBG. In 113 men, HDL2 and HDL3 cholesterol were measured by a precipitation technique. Indian men had a significantly lower HDL-cholesterol concentration than African men (P = 0.003), which is known to be due to a reduction in the HDL3 fraction (demonstrable only in younger men in the subsample drawn for this study). Testosterone did not differ with ethnic group, but SHBG was reduced in Indians (P = 0.03). After allowance for age, ethnic group, alcohol consumption and smoking habit, HDL cholesterol was associated positively with SHBG (P = 0.025) but was not related significantly to either total testosterone or its free and bound components. Serum HDL2 cholesterol was associated positively and independently with SHBG (P = 0.001) and total and bound testosterone (P = 0.002), whereas HDL3 cholesterol showed no significant associations with these factors. Neither SHBG or testosterone afforded an explanation for the relatively low HDL and HDL3 cholesterol concentrations in Indian men.

Alteration of hormone levels in normal males given the anabolic steroid stanozolol

Anabolic steroids have widespread metabolic effects but, to date, their proven clinical indications have been limited. Recently the 17 alpha-alkylated steroid, stanozolol, has been shown to be of value in a variety of commonly occurring vascular diseases. Its endocrine effects have received little attention and we have investigated the effect of administering a 14 d course of stanozolol (10 mg orally per day) on a variety of important hormonal pathways in nine healthy male subjects. Significant changes occurred as follows: a 55% reduction in serum testosterone levels was noted and was accompanied by reductions in 'derived' free testosterone, sex hormone binding globulin and LH levels; total T4 and T3 levels fell in association with a decrease in thyroxine binding globulin, but no alteration was detected in TSH or free T4 levels. Changes in vitamin D status, with falls in 25-hydroxycholecalciferol and vitamin D binding globulin were also observed. These effects were reversible on stopping treatment. Stanozolol therapy therefore leads to a number of hormonal changes, probably by an action at both pituitary and hepatic levels.

Neuroendocrine regulation of the corpus luteum in the human. Evidence for pulsatile progesterone secretion

The pattern of episodic gonadotropin release was studied in 15 normal female volunteers during the luteal phase of the menstrual cycle with 24 h of blood sampling for follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels at 10-min intervals. Six subjects (two in the early, two in the mid-, and two in the late luteal phase) also had each of these specimens processed for progesterone levels. A progressive slowing of LH pulsations was present across the luteal phase with the mean LH pulse frequency declining from 15.2 pulses/24 h in the early to 8.4/24 h in the late luteal phase. A trend towards reduction in the amplitude of LH pulses was also observed (12.3 +/- 2.2 SD mIU/ml in the early vs. 8.6 +/- 3.4 mIU/ml in the late luteal phase; NS). In addition, LH pulses of heterogeneous amplitude were identified during the same 24-h study. The mean +/- SD of the larger and of the smaller LH pulses was 16.9 +/- 4.7 and 2.3 +/- 1.0 mIU/ml, respectively (P less than 0.001). While the slowing of the frequency of all LH pulses correlated well (r = 0.80, P less than 0.001) with the day of the luteal phase and poorly with the actual plasma progesterone levels, the incidence of the small LH pulses was highest in the mid-luteal phase and correlated well with the mean progesterone plasma levels (r = 0.63, P less than 0.01). In the early luteal phase, the pattern of progesterone secretion was stable over the 24-h studies and showed no relationship to episodic LH release. In contrast, in the mid- and late luteal phase, plasma progesterone concentrations rapidly fluctuated during the 24-h studies from levels as low as 2.3 to peaks of 40.1 ng/ml, often within the course of minutes. Progesterone increments closely attended episodes of LH release, as documented by the significant (P less than 0.05) cross-correlation between LH and progesterone levels, at time lags of 25-55 min. The results of this study indicate that in the human luteal phase: (a) the frequency of pulsatile release of LH declines progressively and correlates well with the duration of exposure to progressively and correlates well with the duration of exposure to progesterone; (b) the amplitude of LH pulses varies with the appearance of an increased percentage of smaller pulses correlating well with the acute level of progesterone; (c) in the early luteal phase, the pattern of progesterone secretion is stable; (d) in the mid- and late luteal phase, progesterone secretion is episodic, and correlates with LH pulsatile release; and (e) single progesterone estimations in the mid- and late luteal phase do not accurately reflect corpus luteum adequacy.

Studies on the treatment of idiopathic gynaecomastia with percutaneous dihydrotestosterone

We have studied clinical and endocrine parameters in a group (group A) of forth men referred to us because of persistent idiopathic gynaecomastia (of more than 18 months duration), before and during the administration of percutaneous dihydrotestosterone (DHT). The endocrine parameters (testosterone (T), 17 beta-oestradiol (E2), DHT, gonadotrophins (FSH and LH) and prolactin (PRL), were compared to those of control groups of 12 healthy men on DHT therapy (group B) and 10 on placebo (group C). Local administration of DHT was followed by the complete disappearance of gynaecomastia in 10 patients, partial regression in 19 and no change in 11 patients after 4 to 20 weeks of percutaneous DHT (125 mg twice daily). Before treatment the T + DHT/E2 ratio was significantly (P less than 0.001) lower in group A 244 +/- 21 (SEM) than in groups B and C (361 +/- 21) while T, DHT and E2 concentrations were all within the normal range. During DHT treatment plasma hormone levels were measured in 26 patients from group A: DHT levels increases significantly (day 0: 1.63 +/- 0.14 nmol/l; day 15: 12.8 +/- 1.6 nmol/l, P less than 0.001) while T and E2 levels fell significantly (T: day 0: 22.6 +/- 1.2 nmol/l; day 15: 11.0 +/- 1.5 nmol/l, P less than 0.001; E2: day 0: 110.5 +/- 7.12 pmol/l; day 15: 86.79 +/- 9.4 pmol/l, P less than 0.01). The T/E2 ratio decreased from 231 +/- 20 to 164 +/- 27 (P less than 0.05) while the T + DHT/E2 ratio increased significantly (P less than 0.02) to a normal mean value (day 15: 354 +/- 57).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of danazol on pulsatile gonadotropin patterns and on serum estradiol levels in normally cycling women

The effect of danazol on pulsatile luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol (E2) secretion was examined in eight premenopausal women by serial blood sampling on day 10 of the control and first treatment cycles and during 2 subsequent months of treatment. The mean frequency of LH pulses decreased, while the mean pulse amplitude and increment increased (P less than 0.05). The mean LH concentrations were significantly suppressed in four of eight subjects. The mean frequency of E2 pulses, mean increment, and mean integrated area were decreased (P less than 0.05). The mean integrated FSH area did not change significantly during treatment, and we were not able to demonstrate unequivocal FSH pulses. We conclude that danazol in premenopausal women (1) lowers serum E2 concentrations by decreasing the frequency and increment of E2 pulses, (2) prevents compensatory gonadotropin rise, and (3) lowers the frequency but increases the amplitude and increment of LH pulses. The latter change reflects probably divergent effects of the drug on the pituitary and hypothalamus and results in an inconsistent lowering of basal LH levels.

The use and misuse of androgens

Because testosterone is rapidly metabolized by the liver, it is necessary either to administer androgens by injection in the form of testosterone esters that are absorbed slowly into the circulation or to administer by mouth derivatives that are slowly metabolized by the liver. The later derivatives, however, have deleterious side effects that limit their usefulness. Long-acting parenteral androgen esters are the treatment of choice in the replacement therapy of male hypogonadism. Because these esters must be hydrolyzed to the free hormone prior to exerting their cellular actions the effectiveness of therapy can be monitored by following plasma testosterone levels. All known effects of the endogenous hormone can be duplicated except for the induction and maintenance of normal spermatogenesis. Androgens have been tried in a variety of clinical situations other than male hypogonadism in the hopes that the nonvirilizing actions would outweigh any detectable side effects. The only disorders in which a salutary effect has been documented are hereditary angioneurotic edema and some patients with anemia due to failure off the bone marrow.

The effect of synthetic androgens on the hypothalamic-pituitary-gonadal axis in boys with constitutionally delayed growth

Serial concentrations of basal serum LH, FSH, testosterone, and LH and FSH responses to intravenous gonadotropin-releasing hormone were measured before and during six months of administration of fluoxymesterone or oxandrolone in 14 boys with constitutionally delayed growth and adolescence, in order to assess the effects of these androgens on maturation of the hypothalamic-pituitary-gonadal axis. Before therapy all boys had normal hormonal responses based on bone age. At the end of six months therapy 10 of the 14 boys had lower LH responses (34 to 89% reduction) to GnRH without consistent changes in FSH responses. With both androgens, there there was significant suppression of both basal serum FSH and testosterone. Eleven boys were restudied six months after completion of therapy; basal serum LH, FSH, and testosterone and responses to GnRH were equal to or greater than pretreatment levels, indicating recovery or progressive maturation of the HPGA. All boys had increased growth velocity and imporved weight gain without excessive bone age advancement; all had improved psychosocial adjustment.