Sexual dimorphism in postnatal gonadotrophin levels in infancy reflects diverse maturation of the ovarian and testicular hormone synthesis.

BACKGROUND: The postnatal gonadotrophin surge is sexually dimorphic: FSH levels predominate in girls and LH levels in boys. However, in preterm (PT) girls, both gonadotrophin levels are higher than in PT boys. OBJECTIVE: To evaluate how gonadal maturation contributes to the sex differences in FSH and LH. DESIGN: Monthly follow-up of 58 full-term (FT, 29 boys) and 67 PT (33 boys) infants from 1 week (D7) to 6 months of age (M1-M6). Analyses were also carried out according to postmenstrual (PM) age in PT infants. METHODS: Urinary LH, FSH, oestradiol (E2), testosterone (T) and serum inhibin B (InhB) levels. RESULTS: High gonadotrophin levels in PT girls abruptly decreased (P < .001) by M2, corresponding to a PM age of 38-42 weeks, and LH levels fell below the levels found in boys. This decrease was parallel to a steep increase in E2 levels (P < .001), and, from M4 to M6, LH and E2 correlated positively in PT girls (P < .01). T levels in PT boys increased earlier than E2 levels in PT girls. In addition, InhB levels were high in PT boys already at D7, in contrast to low InhB in PT girls. InhB and FSH correlated negatively in the whole group (P < .001). CONCLUSIONS: Ovarian hormone synthesis is immature and incapable of responding to gonadotrophin stimulus before 38-42 PM weeks in PT girls, which may explain their highly elevated FSH and LH levels. The higher InhB levels in boys compared to girls may explain sexual dimorphism in FSH levels.

Clinical implications of ovarian reserve testing.

Serum and urinary markers of ovarian reserve, follicular phase inhibin B, follicle stimulating hormone, and antimullerian hormone levels, are physiologically associated with ovarian aging, decline with chronologic age, and appear to predict later stages of reproductive aging including the menopause transition and menopause. In infertile women, they can be used to predict low oocyte yield and treatment failure in women undergoing in vitro fertilization. These markers seem to be affected by common ovarian toxicants, such as smoking, which advance the age at menopause. Although available for commercial use, home test kits have not been shown to predict fertility or infertility in the general population. Clinical use of these markers is limited by the variety of assays, lack of definitive thresholds, and their intercycle variability in older women. Results should be conveyed with caution when highly discrepant with age, in the obese, and in women with irregular menstrual cycles. Further research is needed to assess their predictive value for determining fertility in the general population.

Placental production and maternal serum and urine levels of inhibin A and activin A are modified by antihypertensive therapy in hypertensive disorders of pregnancy.

OBJECTIVE: Levels of inhibin A and activin A are raised in pre-eclampsia (PE) but it is not known if antihypertensive therapy can affect their levels. Our aim was to investigate the effect of the antihypertensive drug alpha-methyldopa on serum, urine and placental concentrations of inhibin A and activin A in women presenting with hypertensive disorders of pregnancy. DESIGN: This was a cross-sectional study. PATIENTS: We recruited 65 women presenting with PE, 39 with gestational hypertension (GH) and 104 normotensive controls matched for maternal age, gestational age and parity. MEASUREMENTS: Using specific validated ELISAs, serum and urine levels of inhibin A and activin A, and uterine artery Doppler indices, were measured before and 24-48 h after initiating alpha-methyldopa therapy in women with PE, with GH and controls. Protein extracts were obtained from samples of placental tissue from another group of women with PE, GH and controls for the same analysis. RESULTS: In PE, but not GH, alpha-methyldopa therapy was associated with significantly (P < 0.05) lower levels of both serum and urine inhibin A and activin A. Similarly, in PE but not GH, alpha-methyldopa therapy was associated with lower placental levels of both markers (P < 0.05). There was no significant difference in pulsatility index following treatment in either PE or GH. CONCLUSIONS: Our data indicate that antihypertensive therapy with alpha-methyldopa may have an effect on the synthesis and/or release of placental proteins in pregnancies complicated by PE and that this effect may be independent of its known antihypertensive action.

Serum and urine inhibin A but not free activin A are endocrine biomarkers of severe pre-eclampsia.

OBJECTIVE: Elevation of total serum inhibin A and activin A has been interpreted as evidence of placental dysfunction in women who develop pre-eclampsia. We sought to evaluate serum and urine levels of inhibin A and free activin A in normal and hypertensive pregnancies. STUDY DESIGN: Inhibin A and free activin A were measured by immunoassay in simultaneously collected serum and urine samples from 75 women: (1) severe pre-eclampsia (n = 30); (2) mild pre-eclampsia (n = 11); (3) chronic hypertension (n = 9); (4) pregnant control women (n = 16); and (5) nonpregnant control women (n = 9). Urine levels were normalized to milligrams urine creatinine, and fractional excretions were calculated. RESULTS: Serum and urine inhibin A were increased and fractional excretion was decreased in pregnancy. Serum, urine, and fractional excretion of inhibin A were increased in severe pre-eclampsia, compared with other gravidas. The only difference observed in free activin A was a decrease in serum free activin A in chronic hypertension, compared with severe pre-eclampsia and pregnant control women. Urine inhibin A showed the greatest discrimination between severe pre-eclampsia and pregnant control women: a cut-off of 45 pg/mg urine creatinine had 96.8% sensitivity, 87.5% specificity, and 93.6% accuracy. Women with urine inhibin A greater than 90 pg/mg urine creatinine had a 17-fold relative risk (95% confidence interval 9.7-459.5) of a clinically indicated delivery due to pre-eclampsia. CONCLUSION: Serum and urine levels of inhibin A are altered in severe pre-eclampsia. Urine inhibin A may have application in the diagnosis and management of pre-eclampsia. Those with chronic hypertension have lower serum but not urine free activin A levels, compared with severe pre-eclampsia and mild pre-eclampsia.

Uterine vein and maternal urinary levels of activin A and inhibin A in pre-eclampsia patients.

OBJECTIVES: The aims of this study were to investigate if (i) urinary concentrations of activin A and inhibin A are altered in pre-eclampsia (PE) and (ii) to study the relationship between uterine vein and peripheral vein concentrations of these hormones in PE patients. DESIGN AND METHOD: In a retrospective study, maternal peripheral vein and uterine vein serum and maternal urine samples collected at the time of delivery were analysed. There were three groups of patients; (i) group 1: term normal pregnancies (n = 19) (ii) group 2: patients who developed PE < or = 37 weeks (n = 17) and (iii) group 3: patients who developed PE 37-40 weeks (n = 8). Serum and urinary activin A, follistatin, inhibin A and pro alpha C and urinary creatinine levels were measured using enzyme immunoassays in the laboratory. RESULTS: Normal pregnant urine samples had very low levels of activin A and inhibin A. Both groups 2 and 3 PE patients had significantly higher levels of inhibin A (P < 0.001) and activin A (P < 0.001) compared to the controls. Pro-alpha C was not altered and follistatin was below the detection limit of the assay in the urine. Maternal peripheral serum activin A and inhibin A were significantly higher in groups 2 (P < 0.001) and 3 (P < 0.05) patients compared to the controls. Pro-alpha C-containing inhibins were higher in group 2 patients (P < 0.05) compared to the controls in the peripheral circulation. Uterine vein serum activin A and inhibin A levels were also significantly higher in groups 2 (P < 0.001) and 3 (P < 0.05) patients compared to the controls. There was a highly significant positive correlation between peripheral and uterine vein serum concentrations of activin A, follistatin, inhibin A and pro alpha C, suggesting the same source for these proteins in PE. CONCLUSION: Urinary activin A and inhibin A are raised in groups 2 and 3 PE patients. The magnitude of rise (> 25-fold) suggests these proteins may rise in patients before the onset of the clinical symptoms of PE. Uterine vein levels of these proteins are also raised in PE.

Production of inhibin forms by the fetal membranes, decidua, placenta and fetus at parturition.

Inhibins are regulators of paracrine and endocrine function during pregnancy, but their intrauterine sites of secretion are not well established. In amniotic fluid, inhibin A-, inhibin B- and inhibin pro-alphaC-containing isoforms were present in high concentrations, whereas in maternal serum, inhibin A and pro-alphaC forms were present in high amounts, with low concentrations of inhibin B. In fetal cord serum, inhibin pro-alphaC was present in all samples, inhibin B was detectable in male but not female fetuses, with no detectable inhibin A in either sex. From cultured explants, both inhibin A and B were secreted by chorion laeve, whereas only inhibin A was secreted by placenta, with both tissues secreting inhibin pro-alphaC. Only low concentrations of both dimeric inhibins and pro-alphaC forms were secreted by decidua parietalis and amnion. The dual perfused placental cotyledon secreted both inhibin A and pro-alphaC into maternal perfusate, but only inhibin pro-alphaC into the fetal circulation and less than to the maternal side. We conclude that trophoblast is the predominant source of dimeric inhibins, but with markedly different secretion depending on its intrauterine location. There was a significant decrease in inhibin A and pro-alphaC in amniotic fluid collected at term active labour compared to elective Caesarean section (P < 0.001). This may reflect a local change in inhibin/activin processing at labour, likely in chorion laeve trophoblast cells, which may be important in the paracrine control of the feto-maternal communication required to maintain pregnancy and initiate labour.

Identification of naturally occurring follistatin complexes in human biological fluids.

Follistatin (FS) binds activin and inhibin proteins. Many organs are sensitive to activin and inhibin; thus the formation of FS-activin/inhibin complexes is important to our understanding of ligand activity. Other investigators studying FS have detected large molecular weight immunoreactive FS bands (greater than the expected molecular weight of FS alone) that have not been well characterized. The goal of this study was to identify naturally occurring FS monomers and FS-activin/inhibin complexes in several organ systems. The pituitary, ovary, kidney, and urine were chosen for this investigation. Molecular masses were assigned to in vitro assemblies of complexes containing recombinant inhibin or activin with FS for comparison with naturally occurring FS forms. The recombinant complex of FS-activin was primarily 97-kDa size, while FS-inhibin complexes were detected in a range of molecular sizes from 66 kDa to 97 kDa, 133 kDa, and > 220 kDa. FS-containing complexes of 66-kDa, 97-kDa, and 133-kDa were identified in the tissues examined and in pregnant urine. Our study points to the assembly of a series of FS-activin/inhibin complexes in a variety of organ systems that may impact upon the available amount of free versus bound (or "complexed") ligand, which must be considered when investigating the biology of activin- or inhibin-responsive cells. In addition, urine may be an important biological fluid that can be used to measure significant changes in circulating FS complexes.

Excretory profile of inhibin-like peptide (ILP) during human menstrual cycle: a probable marker for determination of fertile period.

The excretory profile of inhibin-like peptide (10.4 kDa) and its interrelationship with urinary LH, FSH, oestrone glucuronide (E1G) and pregnanediol glucuronide (PdG) during the menstrual cycle were studied. These hormones/metabolites were estimated in daily early morning urine samples obtained from 20 regularly menstruating women. The data revealed that the excretory profile of inhibin-like peptide (ILP) follows a pattern similar to that of E1G. In 17 cycles, ILP peaked 3-4 days prior to the urinary LH peak. A value of 70 ng/mg creatinine (95th centile of ILP levels obtained between 2 and 4 days prior to urinary LH peak and also 5th centile of peak ILP levels) was considered as an indicator of the start of the fertile period. A value of PdG more than 2 micrograms/mg creatinine on two consecutive days was considered as an end of the fertile period. The entire fertile period could be determined in 18 out 20 cycles when criteria based on ILP and PdG levels were applied (accuracy, 90%), whereas it could be determined in 13 out of 20 cycles when criteria based on E1G and PdG levels were applied (accuracy, 65%). Thus, ILP levels in urine may prove to be one of the signals for determining the start of fertile period.

An enzyme-linked immunosorbent assay for the detection of human seminal plasma inhibin.

A simple and sensitive enzyme-linked immunosorbent assay (ELISA) is described for the measurement of inhibin in urine and seminal plasma. Standards used cover a range from 50 ng to 0.05 ng/0.1 ml with a detection limit of 0.098 ng/0.1 ml. Coefficients of variation for intra-assay precision and for inter-assay precision were obtained and compared favourably with RIA. Given the ease of application, this technique is an useful alternative to existing radioimmuno-assays for this peptide.

Serum and urinary prostatic inhibin-like peptide in benign prostatic hyperplasia and carcinoma of prostate.

The levels of immunoreactive prostatic inhibin-like peptide (PIP), having follicle-stimulating hormone suppressing properties, were estimated in the sera and urine samples of patients with benign prostatic hyperplasia (BPH) and prostatic carcinoma (PC) as compared to age-matched controls. Significantly elevated serum PIP levels in BPH (107.8 +/- 19 ng/ml) and PC (88.7 +/- 9 ng/ml) patients were observed as compared to those in control men (10.2 +/- 1 ng/ml). Unlike serum, in urine high levels of PIP in BPH (294 +/- 49 micrograms/24 h) and extremely low levels in PC (23.6 +/- 5 micrograms/24 h) patients were seen as compared to control values (137.6 +/- 10 micrograms/24 h). Furthermore, striking differences were observed between the urinary PIP levels of BPH and PC patients. The results of the present investigation thus indicate the possible use of urinary PIP as a biological marker for prostate cancer.

Potential application of inhibin in male and female contraception.

After a review of investigations into the possible use of inhibin in the regulation of male and female fertility, briefly described and summarized in this article, the authors conclude that, at least in experimental animals, inhibin causes a significant reduction in testicular and epididymal spermatozoa in the male and luteal phase defect in the female. The precise mechanism by which inhibin brings about these effects is not known at present, and its elucidation will greatly help in the more effective use of inhibin.

Evidence for the prostatic origin of immunoreactive inhibin-like material in human seminal plasma.

Inhibin is defined as a gonadal peptide exerting an inhibitory effect on the secretion of follicle-stimulating hormone (FSH) by the pituitary. Using a radioimmunoassay (RIA) procedure developed for a homogeneous inhibin-like peptide with a molecular weight of 14 000 daltons isolated from human seminal plasma, immunoreactive inhibin-like matrial (ILM) was quantitated in serum, urine and semen of men in order to investigate its origin. Vasectomy did not result in a significant reduction in seminal plasma ILM. Determination of ILM immunoreactivity in ejaculates form normal men and semen samples characterized by prostate-rich and prostate-deficient secretions, indicated high levels of ILM in the prostatic secretions. Immunoreactive ILM levels estimated in different fractions of split ejaculates from normal men paralleled those of zinc and acid phosphatase activity and were significantly higher in fractions representing prostatic secretions compared to those representing the secretions of seminal vesicles. Estimation of ILM in semen, serum and urine from bilaterally gonadectomized men showed that immunoreactive ILM levels remained high after gonadectomy. It is concluded that the bulk of the immunoreactive ILM present in the semen, blood and urine of men is not secreted by the testes. The principal site of origin of this material, at least in semen, appears to be the prostate.

Levels of immunoreactive inhibin-like material in urine during the menstrual cycle.

Using a specific and sensitive radioimmunoassay, the authors determined levels of inhibin-like material in the urine of eight healthy women with normal menstrual cycle length of 28 +/- 4 days. The results revealed a cyclic variation in urinary immunoreactive inhibin levels during the menstrual cycles, with a sharp rise in levels three to four days prior to luteinizing hormone (LH) and follicle-stimulating hormone (FSH) peaks. These levels of immunoreactive inhibin may thus serve as a parameter to detect impending LH surge.

PIP: Using a specific and sensitive radioimmunoassay, the authors determined the levels of inhibinlike material in the urine of 8 healthy women with normal menstrual cycle length of 28 +or- 4 days. The results revealed a cyclic variation in urinary immunoreactive inhibin levels during the menstrual cycles, with a sharp rise in levels 3-4 days prior to luteinizing hormone (LH) and follicle-stimulating hormone peaks. These levels of immunoreactive inhibin may thus serve as a parameter to detect impending LH surge.