Human prolactin was measured in plasma by radioimmunoassay at 20 minute intervals for a 24-hour period in each of six normal adults, whose sleep-wake cycles were monitored polygraphically. A marked diurnal variation in plasma concentrations was demonstrated, with highest values during sleep; periods of episodic release occurred throughout the 24 hours.

An analysis of 235 patients with galactorrhea (5.5 per cent males) showed that 20 per cent of all patients, and 34 per cent of women with associated amenorrhea, had radiologically evident pituitary tumors; these patients had the highest serum prolactin concentrations. The largest single group (32 per cent) consisted of women with idiopathic galactorrhea without amenorrhea; prolactin was normal in 86 per cent of these cases. Five patients had the empty-sella syndrome. Prolactin response was tested in selected patients by thyrotropin-releasing hormone, chlorpromazine, L-dopa, 24-hour sampling and other means. Tests with thyrotropin-releasing hormone were most useful in identifying patients with pituitary tumors. Surgery and radiotherapy lowered prolactin to a similar degree in patients with tumor, but galactorrhea, and amenorrhea often persisted after treatment. The ergot derivatives, bromergocryptine and lergotrile mesylate, lowered prolactin in all 18 patients with idiopathic hyperprolactinemia or pituitary tumor, stopped galactorrhea in over 50 per cent, restored menses in over 70 per cent, and allowed pregnancy in three.

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