Serum Concentrations of Inhibin B in Healthy Females and Males Throughout Life

OBJECTIVE: To describe the natural history of inhibin B throughout life according to sex, age, and pubertal development.

METHODS: Based on serum samples from 2707 healthy controls aged 0 to 80 years, sex- and age-specific reference ranges of inhibin B concentrations were constructed. Concentrations were evaluated according to pubertal development and use of oral contraceptives (OCs). Also, measurements from 42 patients with Klinefelter syndrome were included.

RESULTS: In both sexes, inhibin B concentrations were high during minipuberty, decreased in childhood, and significantly increased from Tanner stages B1 to B3 (peak: B4) in females and from G1 to G3 (peak: G3) in males. Despite variations in menstruating females, inhibin B concentrations remained relatively constant after puberty until becoming unmeasurable at menopause. Despite a modest decrease, the inhibin B concentration in males remained relatively high from puberty onward. At any age, males had highest concentrations. Inhibin B SD scores were lower in OC users (median SD score = -0.88) than in nonusers (SD score = 0.35), P < .001. In patients with Klinefelter syndrome, inhibin B concentrations spanned the reference range until approximately 15 years of age, where they decreased to subnormal or unmeasurable levels.

CONCLUSION: Valuable sex- and age-specific reference data for inhibin B concentrations were provided. In OC users, decreased concentrations of inhibin B underlined the ovaries as the only place of inhibin B production. In patients with Klinefelter syndrome, the decline in inhibin B concentrations at puberty underlined the shift in regulation of inhibin B production at pubertal onset.