In men, the normal range of plasma LH, determined by radioimmunoassay, is 5ΓÇô20iu/l, using the NIH reference standard LER-907. Bioactive LH may be detected when immunoreactive LH is immeasurable. Using LER-907 as the radioimmunoassay standard, normal FSH in adult men is also shown to range from 5 to 20iu/l. Pulsatile secretion is less pronounced for FSH. The normal range for plasma testosterone in adult men, determined by radioimmunoassay, is 10ΓÇô35nmol/l (300ΓÇô1,000ng/dl). Free testosterone concentrations can be measured by equilibrium dialysis. Dihydrotestosterone, as measured by radioimmunoassay, averages approximately ten per cent of the testosterone value.
