Differential effect of glucocorticoids on synthesis and secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH)

Glucocorticoid Regulation of Reproduction

It is well accepted that stress, measured by increased glucocorticoid secretion, leads to profound reproductive dysfunction. In times of stress, glucocorticoids activate many parts of the fight or flight response, mobilizing energy and enhancing survival, while inhibiting metabolic processes that are not necessary for survival in the moment. This includes reproduction, an energetically costly procedure that is very finely regulated. In the short term, this is meant to be beneficial, so that the organism does not waste precious energy needed for survival. However, long-term inhibition can lead to persistent reproductive dysfunction, even if no longer stressed. This response is mediated by the increased levels of circulating glucocorticoids, which orchestrate complex inhibition of the entire reproductive axis. Stress and glucocorticoids exhibits both central and peripheral inhibition of the reproductive hormonal axis. While this has long been recognized as an issue, understanding the complex signaling mechanism behind this inhibition remains somewhat of a mystery. What makes this especially difficult is attempting to differentiate the many parts of both of these hormonal axes, and new neuropeptide discoveries in the last decade in the reproductive field have added even more complexity to an already complicated system. Glucocorticoids (GCs) and other hormones within the hypothalamic-pituitary-adrenal (HPA) axis (as well as contributors in the sympathetic system) can modulate the hypothalamic-pituitary-gonadal (HPG) axis at all levels-GCs can inhibit release of GnRH from the hypothalamus, inhibit gonadotropin synthesis and release in the pituitary, and inhibit testosterone synthesis and release from the gonads, while also influencing gametogenesis and sexual behavior. This chapter is not an exhaustive review of all the known literature, however is aimed at giving a brief look at both the central and peripheral effects of glucocorticoids on the reproductive function.

Influence of paradoxical sleep deprivation and sleep recovery on testosterone level in rats of different ages

This study was performed to assess serum testosterone alterations induced by paradoxical sleep deprivation (PSD) and to verify their attenuation during sleep recovery (SR) based on different durations and ages. Wistar male rats aged 12 weeks for the younger group and 20 weeks for the elder group were randomly distributed into one of the following groups: a control group (cage and platform), 3-day SD, 5-day SD, 7-day SD, 1-day SR, 3-day SR and 5-day SR groups. For PSD, the modified multiple platform method was used to specifically limit rapid eye movement (REM) sleep. Differences in the testosterone and luteinizing hormone levels between the younger group and the elder group according to duration of PSD and SR recovery were analysed. Testosterone continued to fall during the sleep deprivation period in a time-dependent manner in both the younger (P=0.001, correlation coefficient r=-0.651) and elder groups (P=0.001, correlation coefficient r=-0.840). The elder group showed a significantly lower level of testosterone compared with the younger group after PSD. Upon SR after 3 days of PSD, the testosterone level continued to rise for 5 days after sleep recovery in the younger group (P=0.013), whereas testosterone concentrations failed to recover until day 5 in the elder group. PSD caused a more detrimental effect on serum testosterone in the elder group compared to the younger group with respect to decreases in luteinizing hormone (LH) levels. The replenishment of serum testosterone level was prohibited in the elder group suggesting that the effects of SD/SR may be age-dependent. The mechanism by which SD affects serum testosterone and how age may modify the process are still unclear.

Serum testosterone levels after cardiac transplantation

BACKGROUND

Men undergoing heart transplantation during the early 1990s had declines in testosterone associated with rapid bone loss. It is unclear whether low testosterone still occurs in an era of lower prednisone doses, whether cyclosporine A (CsA) contributes, whether hypothalamic-pituitary-gonadal (HPG) suppression or direct testicular effects are responsible, and whether low testosterone influences bone loss in men receiving therapy to prevent osteoporosis.

METHODS

Serum testosterone, estradiol, sex hormone binding globulin, gonadotropins, and bone density were measured and prednisone and CsA doses and levels for the first 2 years after transplantation were recorded in a more recently transplanted cohort of 108 participants in a trial comparing alendronate and calcitriol for prevention of posttransplant osteoporosis.

RESULTS

Total and free testosterone levels were lowest during the first month (257+/-131 and 6.2+/-3 ng/dL, respectively) and normalized by 2 months. Gonadotropins were low in the majority, suggesting HPG suppression. Low total testosterone persisted in 14% at 1 year and 18% at 2 years. Prednisone was the major predictor of serum testosterone. No adverse effect of CsA and no relationship between serum testosterone and bone density change were detected.

CONCLUSIONS

Low serum testosterone levels still occur in the early posttransplant period, probably related to HPG suppression by prednisone rather than direct testicular effects of CsA. They are not associated with bone loss in men receiving therapies to prevent osteoporosis. At later time points, low testosterone levels are common and apparently related to primary gonadal dysfunction, suggesting that long-term male heart transplant recipients should be evaluated for hypogonadism.

Different stress modalities result in distinct steroid hormone responses by male rats

Since both paradoxical sleep deprivation (PSD) and stress alter male reproductive function, the purpose of the present study was to examine the influence of PSD and other stressors (restraint, electrical footshock, cold and forced swimming, N = 10 per group) on steroid hormones in adult Wistar male rats. Rats were submitted to chronic stress for four days. The stressors (footshock, cold and forced swimming) were applied twice a day, for periods of 1 h at 9:00 and 16:00 h. Restrained animals were maintained in plastic cylinders for 22 h/day whereas PSD was continuous. Hormone determination was measured by chemiluminescent enzyme immunoassay (testosterone), competitive immunoassay (progesterone) and by radioimmunoassay (corticosterone, estradiol, estrone). The findings indicate that PSD (13.7 ng/dl), footshock (31.7 ng/dl) and cold (35.2 ng/dl) led to lower testosterone levels compared to the swimming (370.4 ng/dl) and control (371.4 ng/dl) groups. However, progesterone levels were elevated in the footshock (4.5 ng/ml) and PSD (5.4 ng/ml) groups compared to control (1.6 ng/ml), swimming (1.1 ng/ml), cold (2.3 ng/ml), and restrained (1.2 ng/ml) animals. Estrone and estradiol levels were reduced in the PSD, footshock and restraint groups compared to the control, swimming and cold groups. A significant increase in corticosterone levels was found only in the PSD (299.8 ng/ml) and footshock (169.6 ng/ml) groups. These changes may be thought to be the full steroidal response to stress of significant intensity. Thus, the data suggest that different stress modalities result in distinct steroid hormone responses, with PSD and footshock being the most similar.

Influence of paradoxical sleep deprivation and cocaine on development of spontaneous penile reflexes in rats of different ages

Recent studies have established that paradoxical sleep deprivation (PSD) and cocaine administration induce genital reflexes (penile erection and ejaculation) in adult and old rats. To determine whether the same effects would induce spontaneous genital reflexes in rats of different ages (30-90 days old), we administered with cocaine (7 mg/kg) or saline to rats after a 4-day period of PSD, or at the equivalent time-point in control animals, and penile erection and ejaculation were then evaluated. In PSD rats administered cocaine, erection was observed from 30 days old to 90 days old, when both genital reflexes reached a peak. Animals submitted to PSD and saline injection showed erection from 60 to 90 days old. None of the control (saline and cocaine) groups of any age displayed these behaviors. The effects of PSD on steroid hormone levels showed that, although testosterone levels increased with age, PSD caused a marked decrease in testosterone at all ages evaluated. Progesterone and corticosterone levels were higher in PSD groups than in the respective control groups. These findings suggest that the interaction of PSD and cocaine probably enhances dopaminergic transmission in the brain and may accelerate the development of genital reflexes in male rats.

Dexamethasone or triamcinolone increases follicular development in immature female rats

We have previously reported that dexamethasone increased follicle-stimulating hormone (FSH) secretion via suppression of inhibin in immature female rats. In the present study, we investigated the effects of dexamethasone or triamcinolone on follicular development and ovarian functions (estradiol and inhibin secretion) in equine chorionic gonadotropin (eCG)-primed immature female rats. Dexamethasone significantly increased the number of ovulated oocytes in immature female rats treated with 5 i.u. eCG. Serum concentration of FSH in eCG-treated female rats was increased by administration of dexamethasone or triamcinolone, showing the peak value at 9 h after its administration, although the levels of inhibin markedly decreased at that time. Serum concentrations of inhibin and estradiol in eCG-treated female rats increased at 24 h after administration of dexamethasone or triamcinolone. These results demonstrate that dexamethasone or triamcinolone increases FSH secretion, and the excess amount of FSH strongly stimulates follicular development cooperating with exogenous eCG.

Dexamethasone increases follicle-stimulating hormone secretion via suppression of inhibin in rats

In the present study, the effects of dexamethasone on follicle-stimulating hormone (FSH) secretion in immature female rats were investigated. Dexamethasone increased the selective secretion of FSH and decreased plasma concentrations of inhibin in immature female rats. The effects of dexamethasone on FSH secretion were not confirmed in rats treated with ovariectomy or immunoneutralization against inhibin. In addition to the direct effect of dexamethasone on FSH synthesis in gonadotrophs, the present study has clearly demonstrated that the increased level of FSH in dexamethasone-treated rats is mediated by suppression of ovarian function, especially by the inhibition of inhibin secretion.

Effect of immobilization stress on testicular germ cell apoptosis in rats

The influence of immobilization stress on testicular germ cell apoptosis was investigated in rats. A transient increase in serum corticosterone and a transient decrease in serum testosterone were observed during each period of immobilization stress. Twenty-four hours after the last immobilization session, the testicular weight and serum concentrations of corticosterone and testosterone were the same between the immobilization stress and control groups. However, the percentages of apoptotic tubules and apoptotic cells in the stress group were significantly higher than those in controls (P < 0.001). These facts suggest that immobilization stress can enhance testicular germ cell apoptosis in rats.

Effects of dexamethasone and dexamethasone plus naltrexone on pituitary response to GnRH and TRH in normal women

The hypothesis that glucocorticoids have a direct central inhibitory effect on the reproductive axis is sutained by the identification of glucocorticoid receptors on GnRH-secreting neurons and gonadotropic pituitary cells. It has been proposed that glucocorticoids and opioids interact centrally in the regulation of the GnRH-LH axis. The inhibitory effect of glucocorticoids may manifest not only directly through the hormone-receptor link, but also indirectly through an increase in opioid tone. The aim of this study was to evaluate the role of glucocorticoids and glucocorticoids combined with an opioid antagonist, in the regulation of basal and GnRH- and TRH-stimulated secretion of LH, FSH and Prl in 7 women with normal menstrual cycles. Blood samples were obtained every 10 min for an hour. GnRH (50 microgram) and TRH (200 microgram) were administered and blood sampling was continued every 15 min for 2 h (day 1). At 5 a.m. the next day, naltrexone (50 mg) was given and at 8 a.m. the GnRH-TRH test was repeated (day 2). At 5 a.m. on day 3, the patients took 2 mg oral dexamethasone and the test was repeated. At 5 a.m. on day 4, the patients took naltrexone and dexamethasone and at 8 a.m. the GnRH-TRH test was repeated. Administration of naltrexone did not cause significant changes in basal concentrations of LH and FSH and their response to GnRH. The area under the curve of the LH response to GnRH on day 3 was significantly less than on days 1, 2 and 4. Administration of naltrexone (day 2) did not cause any significant increase in basal and TRH-stimulated levels of Prl with respect to day 1. On day 3, dexamethasone caused a reduced response of Prl to TRH. Pretreatment with naltrexone (day 4) prevented this reduction. These results suggest that suppression of the response of LH to GnRH induced by dexamethasone may be partly mediated by endogenous opioids. Dexamethasone led to a reduction in the response of Prl to TRH, and naltrexone blocked this suppression. Hence the suppression of Prl and LH by dexamethasone must be partly mediated by endogenous opioids, which must therefore inhibit pituitary secretion of Prl.

Extended clomiphene citrate (CC) and prednisone for the treatment of chronic anovulation resistant to CC alone

OBJECTIVE

To evaluate effectiveness and safety of a regimen of extended clomiphene citrate (CC) and prednisone for patients who fail treatment with CC alone.

DESIGN

Retrospective observational analysis.

SETTING

University-based tertiary infertility center.

PATIENT(S)

Twenty-four anovulatory patients who failed to ovulate after CC 150 mg administered for 5 days.

INTERVENTION(S)

Treatment consisted of CC given on cycle days 3 through 9 (extended) at a starting dose of 100 to 150 mg/d. Additionally, patients were given prednisone 5 mg orally each night throughout the cycle.

MAIN OUTCOME MEASURE(S)

Ovulation was confirmed by luteal serum P. Pregnancy was confirmed by rising hCG levels and transvaginal ultrasound.

RESULT(S)

A total of 60 cycles were available for review. Forty-four of these cycles were ovulatory (73%) and 11 patients (46%) conceived on this therapy. Logistic (two-parameter) pregnancy occurrence over time (cycles) revealed a maximum pregnancy probability of 0.66 and a cycle fecundity of 0.36. No complications of therapy were noted.

CONCLUSION(S)

Clomiphene citrate-resistant anovulatory patients have high rates of ovulation and pregnancy after treatment with extended CC and prednisone. This therapy offers a potential reduction in cost and risk and should be considered in this group of patients before gonadotropin stimulation or surgery.

The luteinizing hormone surge--the final stage in ovulation induction: modern aspects of ovulation triggering

OBJECTIVE

To compile updated information regarding gonadotropin secretion, specifically the physiology of the midcycle LH surge, in natural cycles and under various ovulation induction protocols.

DATA IDENTIFICATION AND SELECTION

Studies that deal with the clinical aspects of LH surge manipulation or substitution were identified through literature and Medline searches.

RESULTS

Three major regulatory factors have been identified as participants in the induction of the midcycle gonadotropin surge. These are hypothalamic GnRH secretion, ovarian and adrenal steroids, and less well-characterized ovarian peptide hormones. Gonadotropin-releasing hormone pulsatility is regulated by a complex mechanism that integrates multiple neurotransmitters and sex steroids. Estradiol plays a central role in the pituitary secretion of LH, which also is influenced by P concentrations. Gonadotropin surge attenuating factor also has been implicated in the regulation of timing and amplitude of the LH surge. Human chorionic gonadotropin is used extensively as a LH surrogate, but its use is associated with a number of disadvantages. Induction of an endogenous LH surge through use of the flare effect of GnRH analogues has been examined more recently and has been found to have several advantages. Recombinant human LH is in the final stages of clinical testing.

CONCLUSION

Although much is known about the physiology of the midcycle LH surge and its variations under different clinical conditions, new approaches to the induction or substitution of the LH surge currently are being examined and learned. The introduction of recombinant gonadotropins into clinical practice is likely to influence ovulation induction and IVF practice to a significant degree in the near future.

Actions of corticotropin-releasing factor or cortisol on follicle-stimulating hormone secretion by isolated pig pituitary cells

This study investigated the direct effects of hydrocortisone (HS), corticotropin-releasing factor (CRF), and adrenocorticotropin (ACTH) on basal and gonadotropin-releasing hormone (GnRH)-stimulated secretion of follicle-stimulating hormone (FSH) from dispersed pig pituitary cells in vitro. Pig pituitaries were dispersed into cells with collagenase, DNAase, and hyaluronidase and then cultured in McCoy's 5a medium containing horse serum (10%) and fetal calf serum (2.5%) pretreated with dextran-coated charcoal for 3 days. Cells were preincubated with steroids, CRF, or ACTH before GnRH was added. HS did not affect basal FSH secretion after 72 h of incubation. Treatment of pituitary cells with increasing concentrations (0.001-800 micrograms/ml) of HS for 72 h resulted in a dose-dependent decrease in GnRH-stimulated FSH release. HS pretreatment did not cause a change in cellular FSH content. Increasing duration (6-72 h) of treatment with HS (200 micrograms/ml) led to a time-dependent decrease in GnRH-stimulated FSH release, achieving statistical significance by 12 h. Porcine ACTH had no influence on basal and GnRH-stimulated FSH secretion. CRF decreased GnRH-stimulated FSH secretion in a dose-dependent manner, and the inhibitory effect required preincubation (6-18 h) with CRF. HS inhibited the FSH secretory responses to phospholipase C, melittin, and 8-bromo-cAMP but did not affect the response to 1,2-dioctanoyl-sn-glycerol and ionophore A23187. These results indicate that both cortisol and CRF can act directly on pig pituitary to inhibit FSH responsiveness to GnRH.

Effect of immobilization stress on testosterone and inhibin in male rats

Adult male Wistar rats were subjected to acute and chronic immobilization stress. Changes in plasma levels of LH, FSH and testosterone and in the content of testicular inhibin and testosterone were studied. Plasma LH levels decreased significantly in response to both acute and chronic stress. Significant decreases in plasma testosterone content were also observed after chronic stress. In contrast, plasma FSH and testicular bioassayable inhibin content did not change after acute or chronic stress. These findings indicate that in male rats immobilization stress induced a dissociation in LH and FSH responses, and decreased testosterone while inhibin remained unaffected.

Dual role of glucocorticoids in regulation of pituitary content and secretion of gonadotropins

To verify the inhibitory effect of cortisol (F) on secretion of luteinizing hormone (LH) 24 h postorchidectomy, we implanted cholesterol (C) or F subcutaneously into male rats, and 4 days later orchidectomized or sham orchidectomized them under ether anesthesia. We injected gonadotropin-releasing hormone (GnRH) or saline into these rats 24 h postorchidectomy, collected blood 30 min later, and measured LH and follicle-stimulating hormone (FSH) in serum and pituitaries. F inhibited GnRH-induced secretion of LH without affecting secretion of FSH. We then implanted C, corticosterone (B), or F into rats, performed the same surgeries, and collected pituitaries 24 h after surgery for quantitation of receptors for GnRH. Neither F nor B affected the number of receptors for GnRH or their affinity for a GnRH analogue. Suppression of LH in serum occurred without decreased pituitary content of LH. In contrast, F increased pituitary content of FSH. Implantation of progesterone in a similar experiment did not affect circulating concentrations or pituitary contents of FSH or LH. These data suggest that glucocorticoids may inhibit responsiveness to GnRH by some mechanism distal to the receptor for GnRH that affects only LH.