Estradiol modulates the pulsatile secretion of biologically active luteinizing hormone in man

Acetate supplementation restores testicular function by modulating Nrf2/PPAR-γ in high fat diet-induced obesity in Wistar rats

Purpose

Several studies have established impaired testicular function in obese male population, including the young males with childhood obesity, contributing to increased male infertility, which is a universal trend in the last few decades. Short chain fatty acids (SCFAs) have been recently demonstrated to inhibit progression to metabolic comorbidities. The present study therefore hypothesized that SCFAs, acetate attenuates testicular dysfunction in high fat diet (HFD)-induced obese rat model, possibly by modulating Nrf2/PPAR-γ.

Methods

Adult male Wistar rats weighing 160-190 g were randomly allotted into three groups (n = 6/group): The groups received vehicle (distilled water), 40% HFD and sodium acetate (200 mg/kg) plus 40% HFD respectively. The administration lasted for 12 weeks.

Results

HFD caused obesity, which is characterized with increased body weight and visceral adiposity and insulin resistance/hyperinsulinemia. In addition, it increased testicular lipid deposition, malondialdehyde, pro-inflammatory mediators, lactate/pyruvate ratio, γ-Glutamyl transferase, and circulating leptin as well as decreased testicular glutathione, nitric oxide, Nrf2, PPAR-γ and circulating follicle stimulating hormone and testosterone without a significant change in testicular lactate dehydrogenase, blood glucose and luteinizing hormone when compared to the control group. Nevertheless, administration of acetate reversed the HFD-induced alterations.

Conclusion

The present results demonstrates that HFD causes obesity-driven testicular dysfunction, associated with testicular lipid deposition, oxidative stress, and inflammation. The study in addition suggests the restoration of testicular function in obese animals by acetate, an effect that is accompanied by elevated Nrf2/PPAR-γ.

MRI findings of nonobstructive azoospermia: lesions in and out of pelvic cavity

Nonobstructive azoospermia (NOA) can be caused by various diseases, including congenital disorders, endocrine disorders, infections, tumor or tumor-like diseases, vascular diseases, etc. Diagnosis of the underlying cause of NOA is complicated and challenging. In this study, we introduce an MR examination protocol for the etiological diagnosis of NOA, and demonstrate a series of NOA patients with different causes and imaging findings. Except for lesions of testes, the patients may also combine abnormalities of adrenal glands and central nervous system. In such cases, the patients could benefit from additional abdominal and intracranial scans.

Anabolic steroid-induced hypogonadism: diagnosis and treatment

OBJECTIVE

To develop an understanding of hypogonadal men with a history of anabolic-androgenic steroid (AAS) use and to outline recommendations for management.

DESIGN

Review of published literature and expert opinions. Intended as a meta-analysis, but no quality studies met the inclusion criteria.

SETTING

Not applicable.

PATIENT(S)

Men seeking treatment for symptomatic hypogonadism who have used nonprescribed AAS.

INTERVENTION(S)

History and physical examination followed by medical intervention if necessary.

MAIN OUTCOME MEASURES(S)

Serum testosterone and gonadotropin levels, symptoms, and fertility restoration.

RESULT(S)

Symptomatic hypogonadism is a potential consequence of AAS use and may depend on dose, duration, and type of AAS used. Complete endocrine and metabolic assessment should be conducted. Management strategies for anabolic steroid-associated hypogonadism (ASIH) include judicious use of testosterone replacement therapy, hCG, and selective estrogen receptor modulators.

CONCLUSION(S)

Although complications of AAS use are variable and patient specific, they can be successfully managed. Treatment of ASIH depends on the type and duration of AAS use. Specific details regarding a patient's AAS cycle are important in medical management.

Role of estrogen receptors and g protein-coupled estrogen receptor in regulation of hypothalamus-pituitary-testis axis and spermatogenesis

Male reproductive function is under the control of both gonadotropins and androgens through a negative feedback loop that involves the hypothalamus, pituitary, and testis known as hypothalamus-pituitary-gonadal axis (HPG). Indeed, estrogens also play an important role in regulating HPG axis but the study on relative contribution to the inhibition of gonadotropins secretion exerted by the amount of estrogens produced within the hypothalamus and/or the pituitary or by the amount of circulating estrogens is still ongoing. Moreover, it is known that the maintenance of spermatogenesis is controlled by gonadotropins and testosterone, the effects of which are modulated by a complex network of locally produced factors, including estrogens. Physiological effects of estrogens are mediated by the classical nuclear estrogen receptor alpha and estrogen receptor beta, which mediate both genomic and rapid signaling events. In addition, estrogens induce rapid non-genomic responses through a membrane-associated G protein-coupled estrogen receptor (GPER). Ours and other studies reported that, in the testis, GPER is expressed in both normal germ cells and somatic cells and it is involved in mediating the estrogen action in spermatogenesis controlling proliferative and/or apoptotic events. Interestingly, GPER expression has been revealed also in the hypothalamus and pituitary. However, its role in mediating estrogen rapid actions in this context is under investigation. Recent studies indicate that GPER is involved in modulating gonadotropin-releasing hormone (GnRH) release as well as gonadotropins secretion. In this review, we will summarize the current knowledge concerning the role of estrogen/estrogen receptors molecular pathways in regulating GnRH, follicle-stimulating hormone, and luteinizing hormone release at the hypothalamic and pituitary levels in males as well as in controlling specific testicular functions such as spermatogenesis, focusing our attention mainly on estrogen signaling mediated by GPER.

Associations between visceral adipose tissue, inflammation and sex steroid concentrations in men

CONTEXT

In men, obesity and the metabolic syndrome are accompanied by decreased testosterone levels, but little is known about the associations between visceral adipose tissue (VAT), VAT-related inflammation and sex steroids.

OBJECTIVE

To examine the relative impact of VAT, abdominal subcutaneous adipose tissue (SAT) and interleukin 6 (IL-6), a marker of VAT-induced inflammation, on testosterone (T) and 17β-oestradiol (E2) levels in dysmetabolic men.

METHODS

We study the NUMEVOX cohort of 229 men, aged 27-77 years, who all had at least one metabolic syndrome criterion (on average three). IL-6, C-reactive protein, Homeostasis Model Assessment of (HOMA) insulin resistance index (HOMA-IR), liver enzymes, E2, LH, sex hormone-binding globulin (SHBG), T, waist circumference and body mass index (BMI) were measured; bioavailable testosterone (BT) was calculated from T and SHBG; MRI-assessed VAT and SAT were analysed in 109 of these men.

RESULTS

Visceral adipose tissue was strongly correlated with E2 (Spearman r = 0.38, P < 0.001) and with BT/E2 ratio (r = -0.42, P < 0.001), while SAT was not correlated with either. IL-6 was correlated with E2 (r = 0.19, P = 0.007), BT (r = -0.19, P = 0.006) and BT/E2 ratio (r = -0.30 P < 0.001). In multivariate linear analysis, the relation between VAT and E2 was independent of age, BMI (P = 0.008), leptin (P < 0.001), T and SHBG. Log(IL-6) was significantly inversely related with log(BT) (P = 0.032) independently of age, VAT, leptin and HOMA-IR.

CONCLUSIONS

17β-oestradiol levels were positively associated with VAT, but not with SAT, while T and BT were negatively and independently associated with IL-6. The significant inverse association between IL-6 and T suggests an important role of low-grade visceral fat inflammation in the central hypogonadism associated with the metabolic syndrome.

Functional relationship between obesity and male reproduction: from humans to animal models

BACKGROUND

The increase in the incidence of obesity has a substantial societal health impact. Contrasting reports have been published on whether overweight and obesity affect male fertility. To clarify this, we have reviewed published data on the relation between overweight/obesity, semen parameters, endocrine status and human male fertility. Subsequently, we have used results obtained in animal models of obesity to explain the human data.

METHODS

Pubmed, Scopus, Web of Science and Google Scholar databases were searched between September 2009 and October 2010 for a comprehensive publication record. Available studies on adult human males were examined. The included animal studies examined obesity and fertility, and focused on leptin, leptin receptor signaling, kisspeptins and/or NPY.

RESULTS

Most overweight/obese men do not experience significant fertility problems, despite the presence of reduced testosterone alongside normal gonadotrophin levels. Only a subgroup of subjects suffers from hypogonadotropic hypogonadism. Animal models offer several explanations and show that reduced leptin signaling leads to reduced GnRH neuronal activity. This may be due to decreased hypothalamic Kiss1 expression, a potent regulator of GnRH/LH/FSH release. As the Kiss1 neurons express leptin receptors, the Kiss1 system may participate in transmitting metabolic information to the GnRH neurons, thus providing a bridge between metabolic regulation and fertility.

CONCLUSIONS

Infertility in overweight/obese males may be explained by leptin insensitivity. This implies a possible role for the KISS1 system in human obesity-related male infertility. If substantiated, it will pave the way for methods to restore fertility in these subjects.

Cross-Talk between Metabolism and Reproduction: The Role of POMC and SF1 Neurons

Energy homeostasis and reproduction require tight coordination, but the mechanisms underlying their interaction are not fully understood. Two sets of hypothalamic neurons, namely pro-opiomelanocortin (POMC) neurons in the arcuate nucleus and steroidogenic factor-1 (SF1) neurons in the ventromedial hypothalamic nucleus, are emerging as critical nodes where metabolic and reproductive signals communicate. This view is supported by recent genetic studies showing that disruption of metabolic signals (e.g., leptin and insulin) or reproductive signals (e.g., estradiol) in these neurons leads to impaired regulation of both energy homeostasis and fertility. In this review, we will examine the potential mechanisms of neuronal communication between POMC, SF1, and gonadotropin-releasing hormone neurons in the regulation of metabolism and reproduction.

Age disrupts androgen receptor-modulated negative feedback in the gonadal axis in healthy men

Testosterone (T) exerts negative feedback on the hypothalamo-pituitary (GnRH-LH) unit, but the relative roles of the CNS and pituitary are not established. We postulated that relatively greater LH responses to flutamide (brain-permeant antiandrogen) than bicalutamide (brain-impermeant antiandrogen) should reflect greater feedback via CNS than pituitary/peripheral androgen receptor-dependent pathways. To this end, 24 healthy men ages 20-73 yr, BMI 21-32 kg/m2, participated in a prospective, placebo-controlled, randomized, double-blind crossover study of the effects of antiandrogen control of pulsatile, basal, and entropic (pattern regularity) measurements of LH secretion. Analysis of covariance revealed that flutamide but not bicalutamide 1) increased pulsatile LH secretion (P = 0.003), 2) potentiated the age-related abbreviation of LH secretory bursts (P = 0.025), 3) suppressed incremental GnRH-induced LH release (P = 0.015), and 4) decreased the regularity of GnRH-stimulated LH release (P = 0.012). Furthermore, the effect of flutamide exceeded that of bicalutamide in 1) raising mean LH (P = 0.002) and T (P = 0.017) concentrations, 2) accelerating LH pulse frequency (P = 0.013), 3) amplifying total (basal plus pulsatile) LH (P = 0.002) and T (P < 0.001) secretion, 4) shortening LH secretory bursts (P = 0.032), and 5) reducing LH secretory regularity (P < 0.001). Both flutamide and bicalutamide elevated basal (nonpulsatile) LH secretion (P < 0.001). These data suggest the hypothesis that topographically selective androgen receptor pathways mediate brain-predominant and pituitary-dependent feedback mechanisms in healthy men.

Obesity and testicular function

Obesity in men, particularly when central, is associated with lower total testosterone [TT], free testosterone [FT] and sex hormone-binding globulin [SHBG], and a greater decline in TT and FT with increasing age compared with lean men. Obesity-related conditions such as obstructive sleep apnea, insulin resistance and type 2 diabetes mellitus are independently associated with decreased plasma testosterone. Possible mechanisms include decreased LH pulse amplitude, inhibitory effects of oestrogen at the hypothalamus and pituitary and the effects of leptin and other peptides centrally and on Leydig cells. Obese men have reduced sperm concentration and total sperm count compared to lean men but sperm motility and morphology appear unaffected. The cause and effect relationships between low plasma androgen levels, obesity and the metabolic syndrome, and associated cardiometabolic risk remain unclear. While weight loss normalizes TT and FT in obese men, androgen replacement in the short term does not significantly improve cardiometabolic risk profile despite reducing fat mass.

Effects of aromatase inhibition on bone mineral density and bone turnover in older men with low testosterone levels

CONTEXT

Aging is associated with declining gonadal steroid production, low bone mineral density (BMD), and fragility fractures. The efficacy and safety of testosterone replacement in older men remains uncertain.

OBJECTIVE

The objective of the study was to assess the effects of aromatase inhibition on BMD in older men with low testosterone levels.

DESIGN AND SETTING

This was a 1-yr, double-blind, randomized, placebo-controlled trial that was conducted at a tertiary care academic center in Boston, MA.

PARTICIPANTS

Participants included 69 men aged 60+ yr with borderline or low testosterone levels and hypogonadal symptoms.

INTERVENTION

Intervention included 1 mg anastrozole daily or placebo.

MAIN OUTCOME MEASURES

Changes in gonadal steroid hormone levels, BMD, and bone turnover markers were measured.

RESULTS

Mean serum testosterone increased from 319 +/- 93 ng/dl at baseline to 524+/-139 ng/dl at month 3 (P < 0.0001) and declined slightly to 474 +/- 145 ng/dl by 1 yr. Estradiol levels decreased from 15 +/- 4 pg/ml at baseline to 12 +/- 4 pg/ml at month 3 and then remained stable (P < 0.0001). Posterior-anterior (PA) spine BMD decreased in the anastrozole group as compared with placebo (P = 0.0014). In the anastrozole group, PA spine BMD decreased from 1.121 +/- 0.141 g/cm(2) to 1.102 +/- 0.138 g/cm(2), whereas in the placebo group, PA spine BMD increased from 1.180 +/- 0.145 g/cm(2) to 1.189 +/- 0.146 g/cm(2). Qualitatively similar, but not statistically significant, changes occurred at the other sites. Bone turnover markers were not affected by anastrozole therapy.

CONCLUSIONS

In older men, aromatase inhibition increases testosterone levels, decreases estradiol levels, and appears to decrease BMD. Aromatase inhibition does not improve skeletal health in aging men with low or low normal testosterone levels.

Anabolic steroid-induced hypogonadism--towards a unified hypothesis of anabolic steroid action

Anabolic steroid-induced hypogonadism (ASIH) is the functional incompetence of the testes with subnormal or impaired production of testosterone and/or spermatozoa due to administration of androgens or anabolic steroids. Anabolic-androgenic steroid (AAS), both prescription and nonprescription, use is a cause of ASIH. Current AAS use includes prescribing for wasting associated conditions. Nonprescription AAS use is also believed to lead to AAS dependency or addiction. Together these two uses account for more than four million males taking AAS in one form or another for a limited duration. While both of these uses deal with the effects of AAS administration they do not account for the period after AAS cessation. The signs and symptoms of ASIH directly impact the observation of an increase in muscle mass and muscle strength from AAS administration and also reflect what is believed to demonstrate AAS dependency. More significantly, AAS prescribing after cessation adds the comorbid condition of hypogonadism to their already existing chronic illness. ASIH is critical towards any future planned use of AAS or similar compound to effect positive changes in muscle mass and muscle strength as well as an understanding for what has been termed anabolic steroid dependency. The further understanding and treatments that mitigate or prevent ASIH could contribute to androgen therapies for wasting associated diseases and stopping nonprescription AAS use. This paper proposes a unified hypothesis that the net effects for anabolic steroid administration must necessarily include the period after their cessation or ASIH.

Effects of aromatase inhibition in hypogonadal older men: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To assess the effects of sustained aromatase inhibition in older hypogonadal men.

DESIGN AND PATIENTS

In a 1-year randomized, double-blind, placebo-controlled trial, 88 men, aged 60 and older with testosterone levels between 5.2 and 10.4 nmol/L on a single measure or between 10.4 and 12.1 nmol/L on two consecutive measures, and symptoms of hypogonadism were recruited. Subjects received either anastrozole 1 mg daily or placebo.

MEASUREMENTS

Changes in gonadal steroid hormone levels, body composition (by computerized tomography (CT) and dual x-ray absorptiometry (DXA)), strength, prostate specific antigen (PSA), symptoms of benign prostatic hypertrophy (BPH), hematocrit and lipid levels were assessed.

RESULTS

Testosterone levels increased from 11.2 +/- 3.3 nmol/L at baseline to 18.2 +/- 4.8 nmol/L at month 3 (p < 0.0001 vs. placebo) while bioavailable testosterone levels increased from 2.7 +/- 0.8 nmol/L at baseline to 5.4 +/- 1.7 nmol/L at month 3 (p < 0.0001 vs. placebo). Testosterone and biotestosterone levels peaked at month 3 and then declined by month 12 (though they remained significantly higher than baseline and greater than placebo). Estradiol levels decreased from 55.8 +/- 15.4 pmol/L at baseline to 42.2 +/- 13.6 pmol/L at month 3 and then remained stable (p < 0.0001). Body composition and strength did not change, nor did PSA, BPH symptoms, hematocrit or lipid levels.

CONCLUSIONS

Anastrozole administration normalized androgen production in older hypogonadal men and decreased estradiol production modestly. These alterations did not improve body composition or strength.

Inhibition of luteinizing hormone secretion by testosterone in men requires aromatization for its pituitary but not its hypothalamic effects: evidence from the tandem study of normal and gonadotropin-releasing hormone-deficient men

CONTEXT

Studies on the regulation of LH secretion by sex steroids in men are conflicting.

OBJECTIVE

Our aims were to determine the relative contributions of testosterone (T) and estradiol (E2) to LH regulation and localize their sites of negative feedback.

DESIGN

This was a prospective study with three arms.

SETTING

The study was conducted at a General Clinical Research Center.

PATIENTS OR OTHER PARTICIPANTS

Twenty-two normal (NL) men and 11 men with GnRH deficiency due to idiopathic hypogonadotropic hypogonadism (IHH) participated.

INTERVENTION

Medical castration and inhibition of aromatase were achieved using high-dose ketoconazole (KC) for 7 d with 1) no sex steroid add-back; 2) T enanthate 125 mg im starting on d 4; or 3) E2 patch 37.5 microg/d starting on d 4. Blood sampling was performed every 10 min for 12 h at baseline, overnight on d 3-4 and d 6-7.

MAIN OUTCOME MEASURES

Mean LH levels, LH pulse amplitude, and GnRH pulse frequency were assessed at baseline, d 3-4, and d 6-7.

RESULTS

In NL men, KC caused a 3-fold increase in mean LH on d 3-4, which was stable on d 6-7 with no add-back. Addition of T reduced LH levels (34.6+/-3.9 to 17.4+/-3.6 IU/liter, P<0.05) by slowing GnRH pulse frequency (13.3+/-0.4 to 6.7+/-1.0 pulses/12 h, P<0.005). LH amplitude increased (6.9+/-1.0 to 12.1+/-1.4 IU/liter, P<0.005). E2 add-back suppressed LH levels (36.4+/-5.6 to 19.0+/-2.4 IU/liter, P<0.005), by slowing GnRH pulse frequency (11.4+/-0.2 to 8.6+/-0.4 pulses/12 h, P<0.05) and had no impact on LH pulse amplitude. In IHH men, restoring normal T levels caused no suppression of mean LH levels or LH amplitude. E2 add-back normalized mean LH levels and decreased LH amplitude from 14.7+/-1.7 to 12+/-1.5 IU/liter (P<0.05).

CONCLUSIONS

1) T and E2 have independent effects on LH. 2) Inhibition of LH by T requires aromatization for its pituitary, but not hypothalamic effects. 3) E2 negative feedback on LH occurs at the hypothalamus.

Interplay between dose and frequency of GnRH administration in determining pituitary gonadotropin responsiveness

BACKGROUND/AIMS

The dose, frequency and contour of GnRH stimulation of the pituitary gonadotrope have been shown to be independent variables influencing pituitary LH secretion. The dynamic interaction between these variables during physiological and pathophysiological states has yet to be examined.

METHODS

Twelve men with GnRH deficiency and idiopathic hypogonadotropic hypogonadism undergoing GnRH therapy participated in a series of studies in which 2 log orders of GnRH doses (2.5-250 ng/kg) were administered at frequencies varying from 0.5 to 8 hourly. Pituitary responses were characterized by pulse amplitudes and nadirs. The relative sensitivity of the gonadotrope to GnRH was defined as that dose of GnRH capable of eliciting an LH pulse amplitude equal to the mean LH amplitude in normal men.

RESULTS

As GnRH stimulation of the gonadotrope slowed from 0.5 to 8 hourly, pulse amplitudes of LH increased whereas mean nadirs decreased (p < 0.05). Unique, curvilinear dose-response curves were found for each frequency that demonstrated an increasing slope (p < 0.03) as the frequency of GnRH stimulation slowed. Thus, the relative sensitivity of the gonadotrope increased as the frequency of GnRH stimulation decreased over the range of physiological frequencies tested.

CONCLUSIONS

We conclude that a delicate interplay exists between the dose and frequency of GnRH stimulation of the gonadotrope that determines pituitary LH gonadotropin responsiveness in the human. Slower frequencies favor increased LH release largely due to decreasing LH nadirs and improved sensitivity of the gonadotropes to GnRH stimulation.

In vitro biological-to-immunological ratio of serum gonadotropins throughout male puberty in children with insulin-dependent diabetes mellitus

Information on the impact of prolonged deficient glycemic control in the quality of the gonadotropin signal delivered by the pituitary gland during puberty in children with insulin-dependent diabetes mellitus (IDDM) is scarce. In the present study, we examined the impact of deficient glycemic control on bioactive LH and FSH concentrations and their corresponding biological-to-immunological (B:I) ratio in boys with poorly controlled, but systemically uncomplicated IDDM. Dual control groups comprising patients with well-controlled IDDM and healthy boys of comparable age and body mass index were included for appropriate comparisons within and between each pubertal stage. Patients with poorly controlled and well-controlled IDDM exhibited serum bioactive FSH levels and B:I FSH ratio similar to those showed by the healthy control group. In contrast, in early and mid-pubertal boys with poorly controlled IDDM bioactive LH levels were normal, but its B:I LH relationship was significantly (P < 0.05) decreased. This attenuation in the quality of the LH signal did not affect total serum T concentrations, and apparently, progression of puberty. Long-standing uncontrolled diabetes and the consequent metabolic disturbances and/or complications may aggravate the reproductive axis dysfunction and eventually provoke pubertal arrest.

Short-term aromatase-enzyme blockade unmasks impaired feedback adaptations in luteinizing hormone and testosterone secretion in older men

The mechanisms subserving hypoandrogenemia and relative hypogonadotropism in older men are not known. The present study tests the clinical hypothesis that aging impairs hypothalamopituitary adaptations to feedback withdrawal induced by antagonism of estrogen biosynthesis. To this end, we appraised gonadal axis responses to estrogen depletion induced by anastrozole (a potent and selective aromatase inhibitor) in nine older and 11 young men vs. placebo in 17 other older and eight young men. The study design comprised a prospectively randomized, double-blind, parallel-cohort intervention. To monitor LH release, blood was sampled every 10 min for 24 h; LH concentrations were assayed by two-site monoclonal immunoradiometric assay; pulsatile LH release quantitated by a model-free discrete peak-detection technique (Cluster); feedback-dependent orderliness of LH secretion via the approximate entropy statistic; and 24-h rhythmicity of LH concentrations by cosine analysis. At baseline, older men had comparable estradiol and testosterone but lower LH concentrations than young controls. Exposure to anastrozole reduced (24-h pooled) serum estradiol concentrations by 50% (P < 0.001) and elevated mean LH concentrations by 2.1-fold (P < 0.001) in both the young and older cohorts. However, older men failed to achieve young adult augmentation of the following: 1) total testosterone concentrations (P < 0.01) or molar testosterone to SHBG ratios (P < 0.01); 2) incremental LH pulse amplitude (P < 0.001) and LH peak area (P < 0.01); 3) mean LH pulse frequency (P = 0.0044); and 4) quantifiable irregularity (approximate entropy) of LH release patterns (P < 0.001). FSH concentrations became comparable in the two age cohorts. In summary, administration of a potent and selective aromatase antagonist reduces estradiol and elevates mean LH concentrations equivalently in young and older men. The low estrogen-feedback state in elderly men unmasks diminished incremental LH pulse amplitude and area; absence of further acceleration of LH pulse frequency; impaired regulation of the orderliness of LH release; and reduced testosterone to SHBG ratios. Thus, aging alters expected hypothalamopituitary-gonadal adaptations to short-term partial estrogen depletion in healthy men.

The effects of cocaine on gonadal steroid hormones and LH in male and female rhesus monkeys

Cocaine stimulates significant increases in estradiol, testosterone (T), and luteinizing hormone (LH) in rhesus monkeys, but the temporal interactions between the gonadal steroid hormones and LH have not been determined. The effects of i.v. cocaine (0.8 mg/kg) or saline placebo administration on estradiol, T, and LH were compared in follicular phase female and male rhesus monkeys. Samples for hormone analysis were collected at 2-min intervals for 20 min, then at 10-min intervals for 50 min. Peak plasma cocaine levels were detected at 4 min and pharmacokinetic analyses showed no significant gender differences. Baseline hormone levels were equivalent before saline and cocaine administration, and saline did not alter LH or estradiol levels. In females, when baseline estradiol levels were low (< 100 pg/ml), LH increased significantly within 8 min after cocaine administration (P < 0.05), but when baseline estradiol levels were high (> 100 pg/ml), LH levels did not change significantly after cocaine administration. Estradiol and T increased significantly after LH, within 16 min after cocaine administration (P < 0.01-0.001). In males, significant LH increases were detected at 16 min after cocaine administration (P < 0.05-0.001), but estradiol and T did not change significantly. Thus, cocaine may stimulate significant increases in estradiol and T in females but not in males. These rapid hormonal changes may contribute to cocaine's abuse-related effects, as well as to disruptions of the menstrual cycle during chronic cocaine administration.

Effects of aromatase inhibition in elderly men with low or borderline-low serum testosterone levels

As men age, serum testosterone levels decrease, a factor that may contribute to some aspects of age-related physiological deterioration. Although androgen replacement has been shown to have beneficial effects in frankly hypogonadal men, its use in elderly men with borderline hypogonadism is controversial. Furthermore, current testosterone replacement methods have important limitations. We investigated the ability of the orally administered aromatase inhibitor, anastrozole, to increase endogenous testosterone production in 37 elderly men (aged 62-74 yr) with screening serum testosterone levels less than 350 ng/dl. Subjects were randomized in a double-blind fashion to the following 12-wk oral regimens: group 1: anastrozole 1 mg daily (n = 12); group 2: anastrozole 1 mg twice weekly (n = 11); and group 3: placebo daily (n = 14). Hormone levels, quality of life (MOS Short-Form Health Survey), sexual function (International Index of Erectile Function), benign prostate hyperplasia severity (American Urological Association Symptom Index Score), prostate-specific antigen, and measures of safety were compared among groups. Mean +/- SD bioavailable testosterone increased from 99 +/- 31 to 207 +/- 65 ng/dl in group 1 and from 115 +/- 37 to 178 +/- 55 ng/dl in group 2 (P < 0.001 vs. placebo for both groups and P = 0.054 group 1 vs. group 2). Total testosterone levels increased from 343 +/- 61 to 572 +/- 139 ng/dl in group 1 and from 397 +/- 106 to 520 +/- 91 ng/dl in group 2 (P < 0.001 vs. placebo for both groups and P = 0.012 group 1 vs. group 2). Serum estradiol levels decreased from 26 +/- 8 to 17 +/- 6 pg/ml in group 1 and from 27 +/- 8 to 17 +/- 5 pg/ml in group 2 (P < 0.001 vs. placebo for both groups and P = NS group 1 vs. group 2). Serum LH levels increased from 5.1 +/- 4.8 to 7.9 +/- 6.5 U/liter and from 4.1 +/- 1.6 to 7.2 +/- 2.8 U/liter in groups 1 and 2, respectively (P = 0.007 group 1 vs. placebo, P = 0.003 group 2 vs. placebo, and P = NS group 1 vs. group 2). Scores for hematocrit, MOS Short-Form Health Survey, International Index of Erectile Function, and American Urological Association Symptom Index Score did not change. Serum prostate-specific antigen levels increased in group 2 only (1.7 +/- 1.0 to 2.2 +/- 1.5 ng/ml, P = 0.031, compared with placebo). These data demonstrate that aromatase inhibition increases serum bioavailable and total testosterone levels to the youthful normal range in older men with mild hypogonadism. Serum estradiol levels decrease modestly but remain within the normal male range. The physiological consequences of these changes remain to be determined.

Mechanisms of hypothalamic-pituitary-gonadal disruption in polycystic ovarian syndrome

Although the pathogenesis of polycystic ovarian syndrome (PCOS) is still controversial, a series of investigations has demonstrated an array of neuroendocrine abnormalities as a major component of the syndrome. From a neuroendocrine perspective, patients with PCOS exhibit an accelerated frequency and/or higher amplitude of LH pulses, augmentation of LH secretory burst mass, and a more disorderly LH release. Elevated in vitro LH bioactivity and a preponderance of basic LH isoforms, which correlate positively with elevated serum 17-hydroxyprogesterone, androstenedione, and testosterone concentrations, also characterize adolescents with PCOS. Heightened GnRH drive of gonadotropin secretion and a steroid-permissive milieu appear to jointly promote elevated secretion of basic LH isoforms. Positive feedback is implied, because hypersecretion of highly bioactive LH in PCOS probably contributes to inordinate androgen output. However, the precise nature of feedback disruption remains uncertain. Indeed, recent data suggest that PCOS is marked by anomalies of both feedforward and feedback signaling between GnRH/LH and ovarian androgens. From a single hormone perspective, the individual patterns of LH and androstenedione release are consistently more irregular in patients with PCOS. Bihormonal analysis has disclosed concomitant uncoupling of the pairwise synchrony of LH and testosterone, LH and androstenedione, and testosterone and androstenedione secretion. The foregoing ensemble of findings points to deterioration of both orderly uniglandular and coordinate bihormonal output in PCOS. Additional studies are needed to establish the primary pathophysiologic mechanisms underlying this disorder.

Five-day pulsatile gonadotropin-releasing hormone administration unveils combined hypothalamic-pituitary-gonadal defects underlying profound hypoandrogenism in men with prolonged critical illness

Central hyposomatotropism and hypothyroidism have been inferred in long-stay intensive care patients. Pronounced hypoandrogenism presumably also contributes to the catabolic state of critical illness. Accordingly, the present study appraises the mechanism(s) of failure of the gonadotropic axis in prolonged critically ill men by assessing the effects of pulsatile GnRH treatment in this unique clinical context. To this end, 15 critically ill men (mean +/- SD age, 67 +/- 12 yr; intensive care unit stay, 25 +/- 9 days) participated, with baseline values compared with those of 50 age- and BMI-matched healthy men. Subjects were randomly allocated to 5 days of placebo or pulsatile iv GnRH administration (0.1 microg/kg every 90 min). LH, GH, and TSH secretion was quantified by deconvolution analysis of serum hormone concentration-time series obtained by sampling every 20 min from 2100-0600 h at baseline and on nights 1 and 5 of treatment. Serum concentrations of gonadal and adrenal steroids, T(4), T(3), insulin-like growth factor I (IGF), and IGF-binding proteins as well as circulating levels of cytokines and selected metabolic markers were measured. During prolonged critical illness, pulsatile LH secretion and mean LH concentrations (1.8 +/- 2.2 vs. 6.0 +/- 2.2 IU/L) were low in the face of extremely low circulating total testosterone (0.27 +/- 0.18 vs. 12.7 +/- 4.07 nmol/L; P < 0.0001) and relatively low estradiol (E(2); 58.3 +/- 51.9 vs. 85.7 +/- 18.6 pmol/L; P = 0.009) and sex hormone-binding globulin (39.1 +/- 11.7 vs. 48.6 +/- 27.8 nmol/L; P = 0.01). The molar ratio of E(2)/T was elevated 37-fold in ill men (P < 0.0001) and correlated negatively with the mean serum LH concentrations (r = -0.82; P = 0.0002). Pulsatile GH and TSH secretion were suppressed (P < or = 0.0004), as were mean serum IGF-I, IGF-binding protein-3, and acid-labile subunit concentrations; thyroid hormone levels; and dehydroepiandrosterone sulfate. Morning cortisol was within the normal range. Serum interleukin-1beta concentrations were normal, whereas interleukin-6 and tumor necrosis factor-alpha were elevated. Serum tumor necrosis factor-alpha was positively correlated with the molar E(2)/testosterone ratio and with type 1 procollagen; the latter was elevated, whereas osteocalcin was decreased. Ureagenesis and breakdown of bone were increased. C-Reactive protein and white blood cell counts were elevated; serum lactate levels were normal. Intermittent iv GnRH administration increased pulsatile LH secretion compared with placebo by an increment of +8.1 +/- 8.1 IU/L at 24 h (P = 0.001). This increase was only partially maintained after 5 days of treatment. GnRH pulses transiently increased serum testosterone by +174% on day 2 (P = 0.05), whereas all other endocrine parameters remained unaltered. GnRH tended to increase type 1 procollagen (P = 0.06), but did not change serum osteocalcin levels or bone breakdown. Ureagenesis was suppressed (P < 0.0001), and white blood cell count (P = 0.0001), C-reactive protein (P = 0.03), and lactate level (P = 0.01) were increased by GnRH compared with placebo infusions. In conclusion, hypogonadotropic hypogonadism in prolonged critically ill men is only partially overcome with exogenous iv GnRH pulses, pointing to combined hypothalamic-pituitary-gonadal origins of the profound hypoandrogenism evident in this context. In view of concomitant central hyposomatotropism and hypothyroidism, evaluating the effectiveness of pulsatile GnRH intervention together with GH and TSH secretagogues will be important.

Aromatase inhibition in the human male reveals a hypothalamic site of estrogen feedback

The preponderance of evidence states that, in adult men, estradiol (E2) inhibits LH secretion by decreasing pulse amplitude and responsiveness to GnRH consistent with a pituitary site of action. However, this conclusion is based on studies that employed pharmacologic doses of sex steroids, used nonselective aromatase inhibitors, and/or were performed in normal (NL) men, a model in which endogenous counterregulatory adaptations to physiologic perturbations confound interpretation of the results. In addition, studies in which estrogen antagonists were administered to NL men demonstrated an increase in LH pulse frequency, suggesting a potential additional hypothalamic site of E2 feedback. To reconcile these conflicting data, we used a selective aromatase inhibitor, anastrozole, to examine the impact of E2 suppression on the hypothalamic-pituitary axis in the male. Parallel studies of NL men and men with idiopathic hypogonadotropic hypogonadism (IHH), whose pituitary-gonadal axis had been normalized with long-term GnRH therapy, were performed to permit precise localization of the site of E2 feedback. In this so-called tandem model, a hypothalamic site of action of sex steroids can thus be inferred whenever there is a difference in the gonadotropin responses of NL and IHH men to alterations in their sex steroid milieu. A selective GnRH antagonist was also used to provide a semiquantitative estimate of endogenous GnRH secretion before and after E2 suppression. Fourteen NL men and seven IHH men were studied. In Exp 1, nine NL and seven IHH men received anastrozole (10 mg/day po x 7 days). Blood samples were drawn daily between 0800 and 1000 h in the NL men and immediately before a GnRH bolus dose in the IHH men. In Exp 2, blood was drawn (every 10 min x 12 h) from nine NL men at baseline and on day 7 of anastrozole. In a subset of five NL men, 5 microg/kg of the Nal-Glu GnRH antagonist was administered on completion of frequent blood sampling, then sampling continued every 20 min for a further 8 h. Anastrozole suppressed E2 equivalently in the NL (136 +/- 10 to 52 +/-2 pmol/L, P < 0.005) and IHH men (118 +/- 23 to 60 +/- 5 pmol/L, P < 0.005). Testosterone levels rose significantly (P < 0.005), with a mean increase of 53 +/- 6% in NL vs. 56 +/- 7% in IHH men. Despite these similar changes in sex steroids, the increase in gonadotropins was greater in NL than in IHH men (100 +/- 9 vs. 58 +/- 6% for LH, P = 0.07; and 85 +/- 6 vs. 41 +/- 4% for FSH, P < 0.002). Frequent sampling studies in the NL men demonstrated that this rise in mean LH levels, after aromatase blockade, reflected an increase in both LH pulse frequency (10.2 +/- 0.9 to 14.0 +/- 1.0 pulses/24 h, P < 0.05) and pulse amplitude (5.7 +/- 0.7 to 8.4 +/- 0.7 IU/L, P < 0.001). Percent LH inhibition after acute GnRH receptor blockade was similar at baseline and after E2 suppression (69.2 +/- 2.4 vs. 70 +/- 1.9%), suggesting that there was no change in the quantity of endogenous GnRH secreted. From these data, we conclude that in the human male, estrogen has dual sites of negative feedback, acting at the hypothalamus to decrease GnRH pulse frequency and at the pituitary to decrease responsiveness to GnRH.

Leptin and androgens in male obesity: evidence for leptin contribution to reduced androgen levels

Leptin circulates in plasma at concentrations that parallel the amount of fat reserves. In obese males, androgen levels decline in proportion to the degree of obesity. Recently, we have shown that in rodent Leydig cells leptin inhibits hCG-stimulated testosterone (T) production via a functional leptin receptor isoform; others have found that leptin inhibits basal and hCG-induced T secretion by testis from adult rats. In this study, we further investigated the relationship linking leptin and androgens in men. Basal and hCG-stimulated leptin and sex hormone levels were studied in a large group of men ranging from normal weight to very obese (body mass index, 21.8-55.7). Initial cross-sectional studies showed that circulating leptin and fat mass (FM) were inversely related with total and free T (r = -0.51 and r = -0.38, P < 0.01 and P < 0.05, respectively). Multiple regression analysis indicated that the correlation between leptin or FM and T was not lost after controlling for SHBG and/or LH and/or estradiol (E2) levels and that leptin was the best hormonal predictor of the lower androgen levels in obesity. Dynamic studies showed that in obese men the area under the curve of T and free T to LH/hCG stimulation (5000 IU i.m.) was 30-40% lower than in controls and inversely correlated with leptin levels (r = -0.45 and r = -0.40, P < 0.01 and P < 0.05, respectively). Also, LH/hCG-stimulation caused higher increases in 17-OH-progesterone to T ratio in obese men than in controls, whereas no differences were observed between groups either in stimulated E2 levels or in the E2/T ratio. In all subjects, the percentage increases from baseline in the 17-OH-progesterone to T ratio were directly correlated with leptin levels or FM (r = 0.40 and r = 0.45, P < 0.01), but not with E2 or other hormonal variables. In conclusion, our studies, together with previous in vitro findings, indicate that excess of circulating leptin may be an important contributor to the development of reduced androgens in male obesity.

Prenatal exposure of female rhesus monkeys to testosterone propionate increases serum luteinizing hormone levels in adulthood

OBJECTIVE

To determine whether prenatal androgenization of the developing primate hypothalamohypophyseal unit induces irreversible changes in LH secretion.

DESIGN

Prospective nonrandomized study.

SETTING

An academic research environment.

ANIMALS

Forty-one adult ovulatory female rhesus monkeys.

INTERVENTION(S)

Seventeen female rhesus monkeys exposed prenatally to testosterone propionate (female pseudohermaphrodites) and 24 normal females underwent blood sampling over two ovulatory menstrual cycles.

MAIN OUTCOME MEASURE(S)

Serum FSH, LH, E2, and T were determined by RIA; P was determined by enzyme immunoassay. Serum bioactive LH was measured by mouse Leydig cell bioassay.

RESULT(S)

Tonic immunoactive LH hypersecretion and normal FSH release occurred in female pseudohermaphrodites compared with normal females. Periovulatory immunoactive LH and FSH secretion was similar in both female types, whereas a relative increase in the amount of circulating bioactive LH to immunoactive LH was found at midcycle in female pseudohermaphrodites versus normal females. The length of the follicular phase was unaffected by prenatal androgen exposure, but the slopes of serum T and E2 concentrations versus follicular phase cycle day were significantly lower in female pseudohermaphrodites than normal females. Luteal phase length and P secretion were comparable in both types of females.

CONCLUSION(S)

Androgen exposure during primate neural differentiation may alter permanently the pattern of LH secretion in the presence of cyclic gonadotropin release.

Neuroendocrine mechanisms mediating awakening of the human gonadotropic axis in puberty

The hypothalamic gonadotropin-releasing hormone (GnRH) pulse generator presides over the pulsatile and feedback-regulated activities of the pituitary-gonadal axis. Awakening of synchronous activity of the GnRH neuronal ensemble in the earliest stages of puberty heralds the onset of full activation of the reproductive axis in girls and boys. Progression from prepuberty to adulthood in boys is directed by marked (30-fold) amplitude enhancement of pulsatile luteinizing hormone (LH) secretion, as assessed by an ultrasensitive immunofluorometric assay and deconvolution analysis. There is a much less apparent rise in LH secretory burst frequency (approximately 1.3-fold increase). Consequently, human puberty is an amplitude-driven neuroendocrine maturational process. However, less is known about pulsatile follicle-stimulating hormone (FSH) release in puberty. Multiple pathophysiologies that result in hypogonadotropic hypogonadism can converge on a final common mechanism of attenuated hypothalamic GnRH pulse generator output and hence reduced LH (and FSH) secretion. Disturbances may take the form of reduced GnRH pulse frequency and/or attenuated GnRH secretory burst mass. When the pathophysiology of hypogonadism originates exclusively in a failed GnRH pulse generator, then either treatment of the primary disease process where possible (e.g., by refeeding in starvation, improved metabolic control in diabetes mellitus, dopamine agonist treatment in hyperprolactinemia, etc) and/or treatment with pulsatile GnRH (e.g., in Kallmann's syndrome, isolated hypothalamic lesions, etc.) can provide relevant therapeutic options in children and adults.

Hormonal evaluation in idiopathic oligozoospermia: correlation with response to clomiphene citrate therapy and sperm motility

The reported response of sperm count to clomiphene citrate therapy in subfertile males with idiopathic oligozoospermia has been widely variable. The author postulates that this may be due in part to patient heterogeneity that may be reflected in pretreatment hormonal status. Seventeen patients with idiopathic oligozoospermia (mean +/- SE sperm density of 7.3 +/- 1.2 x 10(6) sperm/mL, mean FSH of 5 +/- 0.5 IU/L) were studied. Pretreatment basal LH, FSH, testosterone, free T4, and prolactin levels as well as LHRH-stimulated LH and FSH levels were examined in relation to pretreatment semen parameters and percent change in sperm count after a mean of 7.2 +/- 0.6 months of clomiphene citrate therapy. The percentage of motile sperm correlated with basal LH (r = .59, p = .02, n = 16) and free T4 levels (r = .62, p = .02, n = 13). Clomiphene citrate therapy was associated with a significant increase in total sperm count (mean percent change 261 +/- 117, p = .02) and in total motile sperm count (mean percent change 370 +/- 216, p = .03). Percent change in total sperm counts and in total motile sperm counts correlated positively with pretreatment prolactin levels (r = .64, p = .007, n = 16, and r = .62, p = .01, n = 15), but not with the levels of other hormones. The results suggest that in patients with idiopathic oligozoospermia (1) clomiphene citrate therapy may be more effective in the subgroup of patients who have relatively higher prolactin levels, (2) basal and stimulated gonadotropin levels may not be helpful in predicting the response to clomiphene citrate therapy, and (3) lower sperm motility is associated with relatively higher free T4 and lower LH levels. The underlying mechanisms and the clinical utility of the current observations deserve further study.

Estrogen and progesterone receptor mRNA are expressed in distinct pattern in male primate reproductive organs

PURPOSE

The role(s) of estrogens (E) and progesterone (P) in male reproductive physiology remain unclear. Estrogens are used in the treatment of prostatic cancer. Progestins have been used to control excessive sexual behavior in men, and proposed as a male contraceptive. Previous immunohistochemical studies have shown that E receptors (ER) are present in the reproductive tract of male nonhuman primates.

METHOD

We examined the expression pattern of ER and progesterone receptor (PR) mRNA in adult primate male reproductive tract. mRNA was extracted from male pituitary, testis, prostate and different regions of the epididymis of three intact adult cynomolgous monkeys. Ovarian, myometrial and spleen mRNA were used as controls. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to amplify ER and PR mRNA; beta-actin mRNA was used as a reference. Primers for ER, PR and beta-actin were designed using the most conserved areas in the corresponding human cDNA sequences, and the identity of the PCR products was verified using Southern hybridization. Semiquantitative analysis of ER and PR mRNA content in different parts of the male reproductive tract was carried out by spiking the PCR reaction with 33P-dCTP, and amplifying the samples for 20 cycles with the beta-actin primers, whereas 30 cycles were used for ER and PR.

RESULTS

The results are expressed as cpm ratios of ER or PR/beta-actin. All the male reproductive organs studied revealed a strong signal for ER and PR mRNA. The results of the semiquantitative analysis indicate that the expression of both ER and PR was highest in testis (mean +/- SE 6.4 +/- 1.3 and 0.5 +/- 0.1, respectively). The mean figures for prostate were 0.5 and 0.4, respectively. The mean content of ER and PR in the different areas of epididymis was 0.5 and 0.1, respectively. The epididymal ER mRNA was highest in the corpus region (ER/beta-actin 0.7), the ratio being 0.4 for the caput and cauda regions. The expression pattern of PR mRNA was different, and the caput of epididymis being the most intense (0.2). Surprisingly, the pituitary content of ER and PR mRNA was close to that seen in the ovary, the mean +/- SE values being 7.6 +/- 0.5 and 1.3 +/- 0.1, respectively.

CONCLUSIONS

We, therefore, conclude that male monkey reproductive tract contains mRNA for ER and PR, and there appears to be regional variation in their expression. Thus the role(s) of Es and P in male reproductive physiology, specifically in sperm maturation, warrants further investigations.

Effects of oestrogen treatment on serum gonadotrophin bioactivity, immunoreactivity and isohormone distribution, and on immunoreactive inhibin levels, in prostatic cancer patients

OBJECTIVE AND DESIGN

No data are available on effects of long-term exposure to oestrogen on bioactivity of gonadotrophins in men. We studied the effects of a 6-month oestrogen therapy on serum FSH and LH bioactivity (B), immunoreactivity (I) and isohormone distribution, and on serum I-inhibin levels, in patients with prostatic carcinoma.

PATIENTS

Eleven men with advanced prostatic cancer were studied, each receiving 160 mg of polyoestradiol phosphate (Estradurin) once a month intramuscularly for 6 months.

MEASUREMENTS

Serum samples were collected before, and after 2 and 6 months of oestrogen treatment. Serum B- and I-FSH levels were measured by immature rat granulosa cell bioassay and immunofluorometric (IFMA, Delfia) assay, respectively, and those of B- and I-LH by mouse interstitial cell bioassay and IFMA, respectively. Serum oestradiol (E2) concentrations were measured by IFMA assay, and serum testosterone (T) and inhibin levels by radioimmunoassay. Isoelectric focusing was used for fractionation of the FSH and LH isoforms.

RESULTS

The pretreatment levels of B-FSH and I-FSH were 84.7 +/- 21.6 and 11.4 +/- 3.2 IU/l (mean +/- SEM), respectively, and the B/I ratio of FSH was 8.3 +/- 1.0. The pretreatment levels of B-LH and I-LH were 23.5 +/- 3.2 and 10.1 +/- 2.3 IU/l, respectively, and the B/I ratio was 3.0 +/- 0.4. After 6 months of oestrogen therapy, B-FSH and I-FSH decreased to 37.5 +/- 8.1 (P < 0.05) and 1.3 +/- 0.3 IU/l (P < 0.01), respectively, but the B/I ratio of FSH increased to 28.5 +/- 4.2 (P < 0.05). B- and I-LH levels decreased in 6 months to 7.4 +/- 0.9 and 2.3 +/- 0.5 IU/l (P < 0.01), respectively, but no change was found in the B/I ratio of LH. Serum T levels decreased from 19.0 +/- 2.6 to 2.7 +/- 0.9 nmol/l (P < 0.01) during the 6-month treatment, and the respective E2 levels increased from 0.2 +/- 0.01 to 4.4 +/- 0.5 nmol/l (P < 0.01). Serum I-inhibin levels were analysed from eight patients. The levels at 0, 2 and 6 months were 0.81 +/- 0.09, 0.50 +/- 0.03 and 0.54 +/- 0.01 microgram/l, respectively. Gonadotrophins in the pretreatment and 6-month samples of four patients were analysed by isoelectric focusing. In FSH of all subjects, and in LH of three subjects, a shift from acidic to more basic isoforms occurred after oestrogen therapy. This is in keeping with the increase of the B/I ratio of FSH. With LH, the isoform shift occurred between fractions with similar B/I ratios, and hence there was no shift in the overall B/I ratio.

CONCLUSIONS

Oestrogen therapy of men suppressed bioactive and immunoreactive levels of gonadotrophins. The B/I ratio of FSH increased, and this increase was associated with a shift in the isohormone profile to more basic forms. In contrast, no change occurred in the B/I ratio of LH, even though changes in the isohormone profile were observed. Hence, not all changes in the isohormone distribution of gonadotrophins result in changes of the intrinsic in-vitro bioactivity.

Ovarial steroids and methionine-enkephalin modulation of adrenergic transmission in rabbit oviduct

1. The effect of methionine-enkephalin on the [3H]-noradrenaline ([3H]-NA) overflow and on contractions evoked by field electrical stimulation (FES) and by exogenous NA were studied in vitro in the isthmic part of oviduct of rabbits (untreated and treated with estradiol or progesterone). 2. The evoked tritium overflow (which reflected [3H]-NA overflow) was determined by liquid scintillation spectrometry. 3. Field electrical stimulation of 4 Hz (trains of 40 pulses, 0.3 msec) evoked guanethidine-sensitive contractions. 4. In all groups of animals methionine-enkephalin dose dependently decreased FES-evoked contractions but not those evoked by exogenous NA. 5. The amount of tritium overflow evoked by 4 Hz stimulation (600 pulses, 1 msec) was significantly lower in tissues from estradiol treated (1.16 +/- 0.19%) compared with those obtained in tissues from untreated (1.82 +/- 0.22%) and progesterone treated (2.07 +/- 0.21%) rabbits. Methionine-enkephalin, 1 microM, decreased the evoked tritium overflow in the isthmus from untreated rabbits by 36.1 +/- 3.6%, in estradiol treated by 22.8 +/- 2.9% and in progesterone treated by 52.3 +/- 4.5%. 6. The results suggest that the methionine-enkephalin effect on FES-evoked contractions could be due to a prejunctional effect on the adrenergic terminals and that there is a hormonal dependence of the opioid effect on [3H]-NA overflow.

The differential effects of FSH and LH on the human ovary

The basic foundation for normal puberty and adult reproductive function is established during fetal life with the adequate development of the hypothalamus, pituitary and gonads. Further maturation and differentiation of the hypothalamic-pituitary-gonadal axis continues throughout childhood, puberty, adult life and senescence. Pituitary FSH and LH play a central role in the cascade of events in the hypothalamic-pituitary-gonadal axis by mediating between the brain and hypothalamus on one hand and the end-organ, the ovary, on the other. Absent or low pituitary secretion of FSH and LH, as occurs in hypothalamic/pituitary hypogonadism, leads in women to anovulation, amenorrhoea and absent ovarian follicular development. The ability of gonadotrophins to modulate ovarian function depends on their rate of synthesis by the pituitary gonadotrophs, on their circulating concentrations (which vary throughout life and throughout the menstrual cycle), on the relative abundance of the multiple forms of gonadotrophins that have varying biological activity, on the presence of their receptors on the different cell types of the ovary, on the intracellular adenylate cyclase enzyme that causes the production of cAMP, and on the extra- and intragonadal factors that are able to modulate the effects of gonadotrophins in the ovary. Recent clinical and basic research with recombinant gonadotrophins, molecular biological studies on the localization, function and regulation of the long sought after gonadotrophin receptors, as well as research on the interaction between gonadotrophins and local intragonadal factors have widened our knowledge about the function and role of FSH and LH in the ovary and have provided new insights into previously unanswered questions of ovarian physiology and pathophysiology and will provide the basis for the design of new treatment strategies to overcome ovulatory gonadotrophin-dependent dysfunction in the future.

Effects of ethinyl estradiol on semen quality and various hormonal parameters in a eugonadal male

OBJECTIVE

To determine the influence of estrogens on male fertility.

DESIGN

A 36-year-old eugonadal male was subjected to two different regimens of treatment with ethinyl estradiol (EE2). Sperm quality, immunoreactive luteinizing hormone (LH) and follicle-stimulating Hormone (FSH), testosterone (T), estrone (E1), estradiol (E2), dehydroepiandrosterone sulfate (DHEAS), prolactin (PRL) and sex hormone-binding globulin were determined at intervals of 2 weeks for 315 days.

SETTING

A gender dysphoria clinic.

PATIENT

A transsexual male nurse.

MAIN OUTCOME MEASURES

It was hypothesized (and confirmed) that by comparing the effects of increasing and constant dose of EE2 on fertility parameters, differences in estrogen-sensitivity would show more clearly. Furthermore, this procedure served to find the minimal dose of EE2 for complete testicular suppression.

RESULTS

Low doses of EE2 (20 micrograms/d) had no negative effect on sperm motility and density for a period of approximately 4 weeks, whereas high doses (60 micrograms/d) reduced motility already after a few days and led to a pronounced decrease in sperm density after 2 weeks. After discontinuation of therapy, motility normalized faster than sperm density. Under increasing doses of EE2 there was a constant decrease of FSH that occurred several weeks earlier than that of LH. Under constant dose of EE2 (60 micrograms/d) the decrease of LH was delayed (with respect to FSH) by only a few days. The decrease in T showed a stronger correlation with that of FSH than with that of LH. Volume and fructose content of the seminal fluid correlated with the decrease in T. Rebound effects were observed for FSH, LH, T, and fructose during the therapy-free interval. Ethinyl estradiol therapy had no influence on the serum concentrations of E1, E2, and PRL. Estrone was the dominant estrogen before and after therapy with EE2. Adrenal gland activity was markedly suppressed by EE2, as reflected by the decrease in DHEAS.

CONCLUSION

The suppressive effect of EE2 on FSH and sperm motility was more pronounced and consistent than on LH and sperm density. The T decrease appears to be mainly caused by a direct effect of EE2 on the testes.

Neuroendocrine regulation of pulsatile luteinizing hormone secretion in elderly men

Leydig cell function is driven by LH, secreted in a pulsatile manner by the anterior pituitary in response to episodic discharge of hypothalamic LHRH into the pituitary portal circulation, under control of a yet to be defined neural mechanism, the "hypothalamic LHRH pulse generator". The normal aging process in elderly men is accompanied by a decline in Leydig cell function. Whereas primary testicular factors undoubtedly play an important role in the decrease of circulating (free) testosterone levels with age, recent studies demonstrated that aging also affects the central compartment of the neuroendocrine cascade. Hypothalamic alterations comprise changes in the regulation of the frequency of the LHRH pulse generator with an inappropriately low frequency relative to the prevailing androgen impregnation and opioid tone, and with an increased sensitivity to retardation of the LHRH pulse generator by androgens. As observed by some authors in basal conditions and by others after endocrine manipulations. LH pulse amplitude seems also to be reduced in elderly men as compared to young subjects. This is most probably the consequence of a reduction in the amount of LHRH released by the hypothalamus. Indeed, challenge of the gonadotropes with low, close to physiological doses of LHRH in young and elderly men reveals no alterations in pituitary responsiveness when looking at either the response for immunoreactive LH or bioactive LH. Deconvolution analysis on data obtained after low-dose LHRH suggests a markedly prolonged plasma half-life of LH in elderly men, a finding which may explain the paradoxical increase of mean LH levels in face of the reduced or unchanged frequency and amplitude of LH pulses.

Luteinizing hormone pulsatility in men with damage to the germinal epithelium

Bioactive-LH (B-LH) was measured in plasma by in-vitro bioassay and immunoactive-LH (I-LH) by immunoassay at 10 min intervals for 6 h in five men after standard chemotherapy for Hodgkin's disease. Eleven normal men acted as controls. Follicle-stimulating hormone (FSH) was markedly raised in the treated patients (mean +/- SEM; 12.8 +/- 2.8 vs. 2.7 +/- 0.4 IU l-1, P less than 0.006) reflecting damage to the germinal epithelium. Bioactive (27.4 +/- 2.8 vs. 12.9 +/- 1.3 IU l-1) and I-LH (9.6 +/- 2.0 vs. 4.9 +/- 0.4 IU l-1) were elevated (P less than 0.006) in the patient group whilst testosterone levels (24.0 +/- 3.8 vs. 19.6 +/- 2.4 nmol l-1) were normal. The testosterone I-LH ratio, a putative index of Leydig cell dysfunction, was negatively correlated with FSH levels (r = -0.85, P less than 0.02). Bioactive and I-LH pulse peak amplitude were elevated, as were pulse maxima (P less than 0.05). In contrast, B-LH pulse frequency was similar between the patients (2 pulses per 6 h) and controls (median 2, range 1-3 pulses per 6 h) as was the I-LH pulse frequency (median 2, 1-2 pulses per 6 h in both groups). The mean B:I LH ratios were similar (2.94 +/- 0.09 vs. 2.63 +/- 0.14) in both groups, although the inter-pulse B:I ratio was increased (P less than 0.007) in the patient group.(ABSTRACT TRUNCATED AT 250 WORDS)

Testosterone reduces the bioactivity of luteinizing hormone (LH) in man

The effect of testosterone on LH bioactivity was investigated in six adult men (aged 40-56 years) with primary hypogonadism. Two men received a 400 mg testosterone implant, another two 800 mg, and the final two patients received both doses in consecutive courses separated by at least 4 weeks. Plasma samples, obtained before and at 1, 2, 4, 8, 16 and 24 weeks after treatment, were analysed for bioactive LH by the mouse Leydig cell bioassay, and immunoreactive LH and testosterone (T) by standard radioimmunoassays. The bioactive to immunoreactive (B:I) LH ratio, an index of LH biopotency, was calculated and the results compared with those from a group (n = 17) of healthy adult men. Before treatment, both bioactive and immunoreactive LH levels in the patients were higher and T levels lower than in the normal men (P less than 0.001). The mean +/- SD B:I LH ratio (3.5 +/- 0.6) in the patients was greater (P less than 0.05) than in the controls (2.7 +/- 0.7), indicating that in primary testicular failure, increased amounts of LH with enhanced bioactivity are secreted. Following T administration, a dose-related increase in circulating T and a reciprocal decrease in LH levels was observed between 1 and 16 weeks of treatment. However, there was a more pronounced decline in bioactive rather than immunoreactive LH levels, so that the B:I LH ratios decreased (P less than 0.001) from basal values after treatment. There was a negative correlation (r = -0.82, P less than 0.001) between circulating T levels and B:I LH ratios; the stronger the feedback signal, the lower the B:I LH ratio. It is concluded that testosterone negative feedback modifies not only the quantity but also the biological quality of secreted LH.

Pathophysiological features of the pulsatile secretion of biologically active luteinizing hormone in man

The development of an in vitro bioassay of high specificity, sensitivity and precision for the measurement of low circulating concentrations of biologically active glycoprotein hormones has offered exciting new insights into the in vivo secretion and metabolic clearance of luteinizing hormone (LH) in various pathophysiological states. Moreover, the most recent combined application of the rat interstitial cell testosterone (RICT) bioassay and a novel multiple-parameter deonvolution model has allowed investigators to dissect plasma concentration profiles of bioactive LH into defined secretory bursts, which have numerically explicit amplitudes, locations in time, and durations, and are acted upon by determinable subject- and study-specific endogenous metabolic clearance rates. Here, we have: (i) reviewed the ability of the endogenous GnRH pulse signal to regulate the in vivo secretion of biologically active LH molecules as assessed in the RICT and by deconvolution mechanics; (ii) demonstrated that low-dose exogenous GnRH pulses effectively mimic spontaneous bioactive LH pulsatility; (iii) investigated the role of endogenous androgen and estrogen in modulating bioactive gonadotropin secretion in men and women; and (iv) described significant alterations in endogenous LH bioactivity in puberty and healthy aging.

Hypogonadism following long-term treatment with diethylstilbestrol

The authors describe the abnormalities of gonadal function developing in a patient with prostate cancer who had received estrogen therapy continuously for 6 years. The pretreatment prostate biopsy showed well developed acini consistent with normal androgenization and adenocarcinoma. Twelve years later, 6 years after discontinuation of estrogen treatment, the patient presented with severe hypogonadism, gynecomastia, and primary hypothyroidism. Testicular biopsies showed ghosts of seminiferous tubules with absence of Leydig cells, and prostatic biopsies showed atrophic acini without evidence of malignancy. Despite undetectable serum testosterone levels, serum gonadotropins were inappropriately normal and responded minimally to gonadotropin-releasing hormone (GnRH) administration. Replacement therapy with levothyroxine did not correct gonadal dysfunction. Thus, prolonged estrogen therapy may result in irreversible testicular destruction and loss of the feed-back response of the hypothalamic pituitary gonadal axis.

Bioactive LH in women with polycystic ovaries and the effect of gonadotrophin suppression

Discrepancies between levels of bioactive LH (B-LH) and immunoreactive LH (I-LH) in polycystic ovarian syndrome (PCO) have been reported previously. Serum levels of I-LH, B-LH (by dispersed Leydig cell assay), FSH, oestradiol (E2) and progesterone (Prog) were measured once to three times weekly over 4 weeks in 13 women with classical clinical, ultrasound and endocrine features of PCO. Eleven women attending for infertility but whose profiles when studied three times weekly by combined endocrine and ultrasound assessment were normal and ovulatory served as controls. Seven of the women with PCO were evaluated during and after 3 weeks suppression with ethinyloestradiol (30 micrograms) plus 150 micrograms either of desogestrel or levonorgestrel; two were given both treatments. Both I-LH and B-LH levels were higher in PCO patients (20 +/- SD 5 U/l and 46 +/- 9 U/l respectively, P less than 0.0001), compared with all phases of the normal cycles except the mid-cycle peak. The B-LH to I-LH (B:I LH) ratio in PCO patients (2.5 +/- 0.7) was higher than in all the control cycle phases (P less than 0.05). I-LH, B-LH, B:I LH ratio, FSH and E2 were all suppressed from the second week of oestrogen-progestogen treatment (P less than 0.01) and returned gradually to pretreatment levels by the third or fourth week after suppression. The LH and FSH levels and B:I LH ratio in PCO patients during suppression were comparable with levels in the early and mid-follicular phases of control cycles but the LH/FSH ratio remained significantly raised (P less than 0.01) at 2.3 +/- 0.7.(ABSTRACT TRUNCATED AT 250 WORDS)

Attenuated release of biologically active luteinizing hormone in healthy aging men

To examine the biological quality and physiologically pulsatile mode of endogenous luteinizing hormone release in active, healthy aging men, we used the rat interstitial-cell testosterone in vitro bioassay to probe LH bioactivity in response to (a) endogenous gonadotropin-releasing hormone (GnRH) action (basal pulsatile bioactive LH secretion); (b) exogenous GnRH stimulation (10 micrograms IV pulses); and (c) inhibition of endogenous estrogen negative feedback (treatment with a nonsteroidal antiestrogen, tamoxifen). Basally, some healthy older men exhibited evidence of neuroendocrine dysfunction, reflected by irregular bursts of bioactive LH release followed by transiently low plasma bio:immuno (B:I) LH ratios. However, mean basal plasma bioactive LH concentrations, B:I ratios, and spontaneous LH pulse properties (peak frequency, amplitude, duration, and enhanced B:I ratios within LH peaks) were not altered in older men. On the other hand, augmentation of bioactive LH secretion and enhancement of plasma B:I ratios by pulsed injections of exogenous GnRH were either significantly reduced or absent in older men. In addition, although tamoxifen increased bioactive LH pulse frequency in both age groups and facilitated exogenous GnRH action in some subjects, older men increased their 12-h mean bioactive LH concentrations, B:I ratios, and bioactive LH peak amplitudes to a significantly lesser degree than young men. In summary, young and older healthy men exhibit similar mean basal plasma bioactive LH concentrations and spontaneous LH pulse properties. However, pituitary bioactive LH reserve is markedly attenuated in older men challenged with either exogenous GnRH or antiestrogen. Accordingly, we conclude that healthy aging men manifest an impaired secretory reserve for biologically active LH release.

Pathophysiologic features of episodic gonadotropin secretion in man

Endocrine glands typically signal their remote target tissues by an intermittent, rather than an invariant, pattern of hormone secretion. This pulsatile mode of hormone release is believed to convey significant information to the target cells. This review focuses on the luteinizing hormone pulse signal in man as a paradigm for endocrine glandular signaling in general. In particular, recent developments in our understanding of the pathophysiology of luteinizing hormone secretion in men and women is examined, and illustrate how specific disturbances in neuroendocrine physiology can result in altered reproductive states are illustrated. New models of pituitary-secretary dynamics that are likely to help clarify more subtle defects in fertility regulation in man and experimental animals are suggested.