Prolactin secretion in normal adults is characterized by periods of episodic secretion which increase in magnitude during sleep. In this study, we report the 24-h mean
prolactin concentrations,
prolactin secretory patterns, and associated pituitary
hormone function in nine patients (seven women and two men) with
hyperprolactinemia of diverse etiologies. Four of the women and one of the men had clinically demonstrable
pituitary tumors, one boy had a
hypothalamic tumor, and the three other women had "functional"
hyperprolactinemia. The 24-h mean
prolactin concentrations derived from averaging the 20-min interval samples for 24 h ranged from 28.6 to 1,220 ng/ml. The plasma
prolactin patterns in these patients showed persistence of episodic secretion in all and loss of the normal sleep-wake difference in plasma
prolactin in seven of nine. Three of the patients with
galactorrhea and comparable 24-h mean
prolactin concentrations (58.3, 59.7, and 64.3 ng/ml) showed similar
prolactin secretory patterns despite different etiologic mechanisms. Evaluation of the secretory patterns of
luteinizing hormone (LH) in these patients showed loss of normal pulsatile LH release and a low 24-h mean LH concentration in the patient with the
pituitary tumor, while the two patients without clinically demonstrable
pituitary tumors ("post-pill"
galactorrhea and "idiopathic"
galactorrhea) showed normal LH secretory patterns and 24-h mean LH concentrations. The 24-h mean
cortisol concentrations and secretory patterns were normal in five of the seven patients who had these parameters measured. The patient with the
hypothalamic tumor had a low 24-h mean
cortisol concentration and production rate and absent response to
metyrapone. The patient with "idiopathic"
galactorrhea had an elevated 24-h mean
cortisol concentration but normal
cortisol production rate and urinary 17-hydroxycorticoid excretion.
Growth hormone secretion was abnormal in four of the patients (one with the
hypothalamic tumor and three with
pituitary tumors).
Thyrotropin-releasing hormone (TRH) administration in four patients resulted in normal TSH release in two patients (one of whom developed
galactorrhea after the test), an absent response in the patient with the
hypothalamic tumor, and a blunted response in one of the women with a
pituitary tumor. The two men had low 24-h mean plasma
testosterone concentrations (69 and 30 ng/100 ml) and symptoms of
impotence and loss of libido. Five of the women (four with
pituitary tumors and one with
Chiari-Frommel syndrome) had either low 24-h mean LH concentrations, abnormal LH secretory patterns, or both. These data indicate that patients with
hyperprolactinemia encompassing a varied etiological range frequently show loss of the normal sleep-associated increase in
prolactin secretion as well as abnormalities in the regulation of the other hypothalamic pituitary-regulated
hormones. The finding that the abnormalities in LH,
growth hormone,
thyrotropin, and
cortisol (adrenocorticotrophic) secretion were almost uniformly confined to the patients with the clinically demonstrable hypothalamic or
pituitary tumors suggests that the size of the lesion is the critical factor.