FSH Stimulated Inhibin B in Disorders of Puberty

Background: Predicting puberty is a clinical challenge. Available tests include basal gonadotropins, GnRH and GnRH analogue stimulation test, hCG stimulation test and basal inhibin B(INHB). Unlike GnRH and GnRH analogue stimulated LH, no study has investigated for possibility of rapidly releasable pool of inhibin B from gonads so far. Therefore, in quest of a better diagnostic test present study was undertaken to explore stimulability of inhibin B and if found stimulable, potential role of FSH stimulated inhibin B(FSH-INHB) as marker of entry into puberty. Methods: A total of forty-two subjects fulfilling eligibility criteria were enrolled into this prospective interventional study. Study cohort was divided into Cohort A (Healthy children in puberty; n=26) and Cohort B (Patients of hypogonadotropic hypogonadism; n=16). All participants were subjected to FSH stimulation test and GnRHa stimulation test as per study protocol. Data was analysed for male and female separately. Results: Mean delta change between INHB and FSH-INHB in cohort A (Male; n=18) was 188.8 pg/ml (p value-0.002) while in cohort B(Male; n=8) was 16.64 pg/ml (p value-0.076). Mean delta change in cohort A(Female; n=8) was 1065 pg/ml (p value- 0.023) while in cohort B (Female; n=8) was 9.8 pg/ml (p value-0.128). On ROC analysis, INHB of 68.88 pg/ml in male had 94.4 % sensitivity and 87.5% specificity while 51.47 pg/ml in female had 75% sensitivity and 100% specificity for entry into puberty. Cut off for FSH-INHB were 116.14 pg/ml and 116.50 pg/ml for male and female respectively (100% sensitivity/100% specificity). Conclusion: Inhibin B was stimulable in both male and female after entry into puberty, highlighting the presence of rapidly releasable pool in ovaries and testes. FSH stimulated inhibin B may emerge as promising tool for entry into puberty.