Pituitary-gonadal axis in male undermasculinisation

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Abstract
AIMS To study the value of assessing serum concentrations of luteinising hormone (LH), follicle stimulating hormone (FSH), testosterone, and dihydrotestosterone (DHT) in patients with male undermasculinisation not caused by androgen insensitivity. METHODS A retrospective study of a register of cases of male undermasculinisation (20 with abnormal testes, eight with 5α-reductase deficiency, three with testosterone biosynthetic defects, seven with Drash syndrome, and 210 undiagnosed). RESULTS A human chorionic gonadotropin (hCG) stimulation test was performed in 66 of 185 children with male undermasculinisation. In 41 of 66 patients the dose of hCG was either 1000 U or 1500 U on three consecutive days. The rise in testosterone was related to basal serum testosterone and was not significantly different between the two groups. Testosterone:DHT ratio in patients with 5α-reductase deficiency was 12.5–72.8. During early infancy, baseline concentrations of LH and FSH were often within normal reference ranges. In patients with abnormal testes, median pre-LHRH (luteinising hormone releasing hormone) concentrations of LH and FSH were 2 and 6.4 U/l, respectively, and post-LHRH concentrations were 21 and 28 U/l. An exaggerated response to LHRH stimulation was observed during mid-childhood in children where the diagnosis was not clear and in all children with abnormal testes. CONCLUSIONS The testosterone:DHT ratio following hCG stimulation is more reliable than the basal testosterone:DHT ratio in identifying 5α-reductase deficiency. During infancy, the LHRH stimulation test may be more reliable in identifying cases of male undermasculinisation due to abnormal testes than basal gonadotrophin concentrations. Male undermasculinisation is a common cause of genital ambiguity Investigation of male undermasculinisation requires thorough evaluation using previously published guidelines The hypothalamo–pituitary–gonadal axis is intrinsically active during the first month of life and this is an opportune moment to investigate affected children The hCG stimulation test is useful for studying defects in testosterone synthesis as well as 5α-reductase deficiency The LHRH stimulation test may be more reliable than basal gonadotrophin concentrations at identifying male undermasculinisation due to abnormal testes