Low serum inhibin B concentrations in male survivors of childhood malignancy

The aim of this study was to assess the value of serum inhibin B in detecti ng male gonadal dysfunction in childhood cancer survivors. 27 male postpube rtal (Tanner's pubertal stage G5 or P6) and 12 pubertal (greater than or eq ual to G2) patients were drawn from the endocrine follow-up protocol of chi ldhood cancer patients at the Paediatric Clinic of Turku University Hospita l, Turku, Finland. The average time (mean +/- S.D.) between the diagnosis a nd this study was 11.7 +/- 4.5 years in the postpubertal and 7.0 +/- 3.9 ye ars in the pubertal group.. Serum samples for the determination of follicle -stimulating hormone (FSH), luteinising hormone (LH), oestradiol, testoster one, and inhibin A and B dimers were collected. The demographic factors, pu bertal stage and testicular size of the patient were measured at the same r outine outpatient visit. Serum inhibin concentrations were correlated to te sticular volume and gonadotrophin concentrations. Strong correlations were observed between testicular size (r = 0.80, P < 0.001) or FSH (r = -0.58, P = 0.002) and inhibin B concentration in the postpubertal group. Inhibin A was not detectable (< 2 pg/ml). Testicular volume measurement was accuratel y documented in 21 postpubertal subjects. Patients with small testicles (< 10 ml) had inhibin B concentrations under 42 pg/ml and those whose testicul ar size was over 13 ml had inhibin B concentrations exceeding 100 pg/ml. In all 12 pubertal survivors, serum inhibin B levels were greater than or equ al to 94 pg/ml, except in one case of testicular cancer where inhibin B was 8.1 pg/ml and the FSH concentration was elevated. Inhibin B seems to be an indicator of male gonadal function in postpubertal childhood cancer surviv ors and could be used in the estimation of gonadal function of male survivo rs earlier than testicular volume or semen analyses would be routinely poss ible. However, the correct cut-off level of serum inhibin B, as well as the details of inhibin B physiology during puberty, remain to be determined be fore semen analysis can be replaced by the measurement of inhibin B. (C) 19 99 Elsevier Science Ltd. All rights reserved.