Serum LH and FSH response in four-hour infusions of luteinizing hormone-releasing hormone in normal men, Sertoli cell only syndrome, and Klinefelter's syndrome.

Constant intravenous infusion of 1 mug/min of luteinizing hormone-releasing hormone (LHRH) for 4 hours into normal men produced a biphasic pattern of LH secretion. The initial LH peak occurred 15-45 minutes after the commencement of the infusion, following which LH levels plateaued or declined, subsequently rising as the infusion continued. No biphasic pattern of secretion could be identified for FSH. During the infusion, no consistent testosterone rise could be identified despite significant elevation of LH levels. Similar infusions of LHRH in men with Sertoli cell only syndrome produced exaggerated responses in terms of both LH and FSH. In contrast, a single intravenous bolus of 100 mug/ LHRH produced an exaggerated response in only one of the 3 men studied, suggesting that the prolonged infusion may be a more discerning dynamic test. Four-hour infusions of LHRH in men with untreated Klinefelter's syndrome produced exaggerated responses for both LH and FSH. After 6 weeks of treatment with long-acting testosterone esters administered weekly (250 mg), the exaggerated responses for both FSH and LH were decreased. For LH, the decrease principally affected the initial phase of LH release, and the pattern obtained resembled more closely the biphasic pattern seen in normal men.