Serum Immunoreactive Inhibin Levels Research Articles

Testicular and serum levels of inhibin and expression of inhibin subunit mRNAs are differentially affected by hemicastration in rats of various ages.

Age-related short-term effects of hemicastration on testicular weight, serum FSH, immunoreactive inhibin, LH and testosterone, testicular levels of inhibin subunit mRNA expression, and bioactive and immunoreactive inhibin were studied in rats of 8, 15 and 22 days of age. Hemicastration led to an increased weight of the remaining testis after 24 h in 8- and 15-day-old rats, but not in 22-day-old rats. Serum FSH levels were elevated in all hemicastrated rats after 8 h. However, serum immunoreactive inhibin levels were decreased only after 72 h in 8-day-old rats and after 24 h in 15- and 22-day-old rats. Inhibin alpha-subunit mRNA expression was increased in the testes of hemicastrated rats of 8 and 15 days of age, whereas inhibin beta B-subunit mRNA expression was elevated in the testes of 15-day-old rats but not in those of 8- and 22-day-old rats. The increase in alpha-subunit mRNA content per testis was caused by an increased concentration and increased testicular weight, whereas the increase in beta B-subunit mRNA in the remaining testis parallelled the increased testicular weight, indicating that different mechanisms play a role in the regulation of these mRNAs. In 22-day-old rats, a transiently decreased expression of inhibin beta B-subunit mRNA was observed 8 h after hemicastration.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated serum immunoreactive inhibin levels in peripubertal boys with chronic renal failure

Boys with chronic renal failure have delayed progress through puberty and have raised gonadotrophin and low testosterone levels indicative of disturbed hypothalamo-pituitary-testicular function. Most studies into the mechanisms underlying the dysfunction have concentrated on the LH-Leydig cell interaction. However, it is now possible to probe the FSH-Sertoli cell axis by measuring plasma immunoreactive inhibin, which is a marker of Sertoli cell function. This study investigated the FSH-Sertoli cell (immunoreactive inhibin) axis in boys with chronic renal failure on conservative and dialysis treatment as they progressed through puberty. The effect of renal transplantation in chronic renal failure was also investigated. Blood was drawn at 15-minute intervals between 2000 and 0700 h from 51 boys with chronic renal failure at various stages of puberty. The samples were divided into two pools, corresponding to the hormone secretion in the first and second part of the night. Single blood samples were drawn from a group of normal boys between 0800 and 1000 h. A total of 37 normal boys and 51 boys with chronic renal failure were examined immediately before and during puberty. Of a total of 80 pulse profiles taken in chronic renal failure, 36 were from transplanted and 44 from non-transplanted uraemic subjects. Immunoreactive inhibin, FSH and testosterone were measured using standard radioimmunoassays. The subjects were pooled into pubertal stages I, II/III and IV/V for analysis of hormone data. Early morning levels of immunoreactive inhibin like molecules (i-Inh) rose steadily with pubertal progression for all subject groups, those for boys with chronic renal failure being significantly elevated over normal boys from pubertal stage II/III onwards. Uraemic boys had higher levels than those who had been transplanted at all pubertal stages (P < 0.05). Early morning levels of FSH were significantly higher in uraemic patients with pubertal stages IV/V compared to our normal boys. There were no differences in i-Inh levels in plasma pooled from the samples taken between 2000 and 0115 h and 0130 and 0700 h for either treatment group at any stage of puberty. Testosterone levels rose in the second part of the profile from pubertal stages II/III onwards for both treatment groups. The proportional increase of testosterone was lower by mid puberty in uraemic than in transplanted children (percentage increases of 92 +/- 29 and 569 +/- 190 respectively, mean +/- SEM). i-Inh failed to correlate with FSH at any Tanner stage or for any subject group. Peripubertal boys with chronic renal failure have highly elevated serum immunoreactive inhibin and FSH levels which are partially reduced by renal transplantation. There was no evidence of any relationship between i-Inh and FSH secretion in either normal boys or in uraemic or transplanted boys with the exception of a positive correlation in late pubertal patients after transplantation. Finally, despite problems associated with the current immunoassay for inhibin, this assay may still prove to be a useful marker of Sertoli cell function in testicular pathology.

Immunoreactive inhibin levels during ovarian stimulation may predict granulosa cell maturity.

The aim of the study was to assess whether the immunoreactive inhibin response to ovarian stimulation in polycystic ovarian syndrome was of predictive value for the outcome of ovulation induction. Daily injections of purified FSH (Metrodin, Serono Laboratories, UK) were administered for the purpose of inducing development and ovulation of a single follicle. All patients had anovulatory infertility secondary to polycystic ovarian syndrome and were resistant to clomiphene citrate. Alternate day serum samples were obtained for measurement of gonadotrophins, sex steroids and inhibin by radioimmunoassay. Alternate day ovarian ultrasound scans were carried out to monitor follicular development. There was a high incidence of multiple follicular development (MFD) (10.2 +/- 7.1 (standard deviation) follicles). There was a close relationship between the number of follicles on the day of the ovulatory trigger and serum oestradiol (E2) levels (R = 0.97, P < 0.001). This relationship was not seen with serum immunoreactive inhibin levels (R = 0.31). The cycles were divided into two groups depending whether there was or was not MFD (more than five follicles > 7 mm in diameter on day of hCG administration). The MFD group had 15.6 +/- 8.5 follicles and the non-MFD group 3.2 +/- 1.6 follicles. There was no difference in the circulating E2 concentration (pmol/l) per follicle between the two groups (non-MFD cycles, n = 6,345 +/- 28.9; MFD cycles, n = 8, 308 +/- 40.29). However, the immunoreactive inhibin concentration (U/ml) per follicle was lower, P < 0.001, in the MFD group (4.3 +/- 1.6 vs 6.9 +/- 0.5). The maximum and mean follicle diameter were lower, P < 0.01, in the MFD group (maximum follicle size 16.5 +/- 3.9 vs 21.2 +/- 1.5 mm, mean follicle size 11.5 +/- 2 vs 14.9 +/- 2.3). When individual cycles were examined E2 and immunoreactive inhibin secretion rose in parallel in cycles with less than five follicles with a rapid rise occurring when the follicles reached about 12 mm in diameter. In cycles where there was MFD there was a disparity between E2 and immunoreactive inhibin secretion with E2 levels rising 4.3 +/- 1.4 days before immunoreactive inhibin levels. These data suggest that in cycles where there are multiple small follicles, E2 secretion is maintained whereas immunoreactive inhibin secretion is substantially lower. Thus, in view of the disparity between E2 and immunoreactive inhibin secretion evident in the MFD group, measurement of immunoreactive serum inhibin concentration may be a better indicator of granulosa cell maturity. Immunoreactive inhibin secretion may occur only from healthy mature follicles.

Circadian Rhythm of Serum Immunoreactive Inhibin in Young and Elderly Men

Serum testosterone (T) levels and inhibin levels decline with normal male aging. In addition, in young men, serum T levels demonstrate a circadian variation that is blunted or lost with normal aging. The purpose of this study was to determine whether serum immunoreactive inhibin levels also demonstrate a circadian variation in young men and if normal aging has an effect on the 24 hr serum inhibin pattern. Hourly blood samples were obtained for 24 hr from 7 young (age 25-35 yr) and 7 elderly (age 65-72 yr) healthy men. Serum inhibin and testosterone levels were measured by RIA. Similar to T, serum inhibin levels demonstrated a circadian pattern in young men. Elderly men also demonstrated a circadian rhythm in serum inhibin, with an average amplitude that was not significantly different from that found in young men, despite the fact that the average 24-hr inhibin level in the elderly men was significantly lower than in the young men. These results demonstrate that immunoreactive inhibin, like T, displays a circadian rhythm in the serum of adult men and the inhibin biorhythm is maintained in elderly men.

Circulating Immunoreactive Inhibin, Gonadotropin, and Prolactin Levels during Pregnancy, Lactation, and Postweaning Estrous Cycle in the Rat

Serum inhibin levels were measured by heterologous RIA during pregnancy, lactation, and the post-weaning estrous cycle in the rat and correlated with changes in serum FSH and LH and prolactin. Blood was serially collected by cardiac puncture under light ether anesthesia from adult Sprague-Dawley rats on alternate days throughout the experimental period. For the first 8 days of pregnancy, immunoreactive inhibin levels remained high, then gradually decreased to reach a nadir at Day 16, and subsequently rose steeply until parturition. The pattern of serum immunoreactive inhibin levels during early pregnancy does not support a corpus luteum source and the dramatic rise from Day 16 to Day 22 correlates with the recommencement of follicular development in the ovary. Inhibin levels decreased rapidly on the day after birth and were suppressed until Day 8 of lactation, slowly increasing thereafter to reach a plateau from Day 14 until weaning (Day 22.5 of lactation). These changes in inhibin levels positively correlated with LH and FSH and negatively with prolactin, and are consistent with an ovarian source for inhibin associated with the recommencement of follicular development resulting from the diminution of the suckling stimulus. Immediately after weaning, serum immunoreactive inhibin levels showed a 4-day cyclic pattern corresponding to the estrous cycle identified by vaginal smear. Inhibin levels peaked on the day of proestrus, reached a nadir on the day of estrus, and rose slowly during metestrus and diestrus to a new peak at proestrus. Serum FSH levels showed an inverse correlation to inhibin levels consistent with a feedback relationship with inhibin.

Serum Immunoreactive Inhibin Levels before and after Luteectomy in the Cynomolgus Monkey (Macaca fascicularis)*

Whereas studies in women have demonstrated that serum immunoreactive inhibin concentrations peak during the luteal phase of the menstrual cycle and that the corpus luteum (CL) encodes mRNA for the inhibin subunits, a clear link between the presence of the CL and circulating inhibin has not been established in primates. Therefore, we measured serum immunoreactive inhibin levels in monkeys before and after luteectomy as well as immunoreactive inhibin concentrations and mRNA encoding the alpha-inhibin subunit in luteal tissue. Monkeys were assigned to one of four groups depending on which day of the luteal phase luteectomy was performed: group A, days 4-5; group B, days 7-8; group C, days 9-10; and group D, days 11-12 (the day after the estrogen surge = day 1 of the luteal phase). Daily blood samples were obtained for 3 days before luteectomy, immediately before surgery, and for 2 days after luteectomy. Immunoreactive inhibin concentrations were measured with a double antibody RIA using an antiserum to bovine 31-kDa inhibin, bovine 31-kDa inhibin for iodination, and a human follicular fluid inhibin preparation as standard. Total RNA was isolated from luteal tissue and transferred by Northern blot onto a Zeta-probe membrane. The probe used for hybridization was the PstI/NcoI restriction enzyme fragment (381 basepairs) of alpha-inhibin DNA generated from a human ovarian cDNA library. Serum inhibin concentrations decreased (P less than 0.05) 24 h after removal of the corpus luteum in each of the four groups studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Human chorionic gonadotrophin raises serum immunoreactive inhibin levels in men with hypogonadotrophic hypogonadism

Inhibin is a gonadal glycoprotein hormone involved in the regulation of FSH. To elucidate the regulation of inhibin production we investigated the acute (daily for 1 week) and chronic (9-10 months of follow-up) changes in immunoreactive inhibin, testosterone, LH and FSH levels in the serum of three hypogonadotrophic hypogonadal patients treated first with hCG alone (for 3-6 months) and then hCG combined with FSH (1-5 months). One patient was unexpectedly resistant to gonadotrophin therapy; in the other two, hCG, with or without FSH, caused a rise in inhibin and testosterone, supporting previous observations that LH, as well as FSH, plays a role in the regulation of inhibin or inhibin-related peptides in men.

Concentrations of Immunoreactive Inhibin in Seminal Plasma and Serum from Normospermic, Oligospermic, Vasectomized, Klinefelter's Syndrome, and Sertoli‐cell–only Syndrome Subjects

Semen samples and blood were collected from 57 men: 23 normospermic, 20 oligospermic, 10 vasectomized, two with Klinefelter's syndrome, and two with Sertoli‐cell–only syndrome. Inhibin was measured by radioimmunoassay techniques as reported previously. Immunoreactive inhibin concentrations in seminal plasma were found to be 8000 to 10, 000 times higher than in blood. A significant correlation (P &lt;0.005) was observed between the serum and seminal plasma concentrations in all groups. No direct correlation was observed between immunoreactive inhibin concentrations in serum or semen with number of sperm in the ejaculate or with sperm motility. Seminal plasma and serum immunoreactive inhibin levels in normospermic subjects were significantly higher than in oligospermic, vasectomized, and Klinefelter's syndrome subjects (P &lt;0.001 and &lt;0.01, respectively).