Summary. During an oral glucose tolerance test (OGTT) glucose and insulin levels were measured in 26 patients with prolactin-producing pituitary tumours without growth hormone excess. Basal glucose and insulin levels did not differ from the values of an age-matched control group. After glucose load the hyperprolactinaemic patients showed a decrease in glucose tolerance and a hyperinsulinaemia. Bromocriptine (CB 154), which suppressed PRL, improved glucose tolerance and decreased insulin towards normal in a second OGTT. -Human PRL or CB 154 had no significant influence on insulin release due to glucose in the perfused rat pancreas. -These findings suggest a diabetogenic effect of PRL. CB 154 might be a useful drug in improving glucose utilization in hormone-active pituitary tumours.Key words: Prolactin, insulin release, glucose tolerance, pituitary tumours, pancreas perfusions, bromocriptine.Acute administration of ovine prolactin (PRL) has been shown to influence glucose metabolism in animals [1,2], to impair glucose tolerance in hypopituitary dwarfs and in hypophysectomized juvenile-type diabetics [3], and to stimulate lipid metabolism [4]. In order to study the long term effects of endogenous PRL on glucose tolerance and glucose-induced insulin secretion, patients with hyperprolactinaemia were investigated. In vitro experiments with the isolated perfused rat pancreas were undertaken to elucidate the direct effect of hPRL on insulin release. * Presented in part at the 11 th Annual Meeting of the European Association for the Study of Diabetes (EASD), Munich, September 4-6, 1975, and published in abstract form in Diabetologia 11, 357 (1975) Material aud Methods a. In vivo-StudyFifteen female and 11 male patients with hyperprolactinaemia were studied (Tab. 1). Twenty-four patients had a pituitary tumour, one had a craniopharyngioma and one had anormal sella turcica. A galactorrhoeaamenorrhoea syndrome was observed in 9 women.The average body weight was 13 ± 4 % above the ideal body weight and the average age was 34 ± 2 years (mean ± SEM). None of the patients had elevated plasma growth hormone concentrations. Eighteen patients had blunted hGH-secretion after insulin-induced hypoglycaemia. In six subjects TSH levels before and after TRH stimulation were below the lower limit of detection; six patients showed TSH values which were subnormal and two suffered from primary hypothyroidism. Thirteen had secondary hypogonadism, eleven had a latent or manifest secondary adrenal insufficiency and three had diabetes insipidus. The mean basal PRL level (x ± SEM) measured by radioimmunoassay [5] was 2422 ± 800 ng/ml ranging from 47 to 18 860 ng/ml. Our normal range for men is 8.5 to 25 ng/ml and for women up to 37.5 ng/ml. Fourteen patients were on appropriate hormone replacement therapy at the time of the study. Hypothyroidism was treated in all cases except two (Tab. 1) in order to avoid effects of low thyroid hormone levels on glucose tolerance.Fifteen patients (nine females and six males) were treated with bromocripti...
Human prolactin (hPRL) is the most recent anterior pituitary hormone in human endocrinology, whose structure has been elucidated in 1977. The possibility to measure hPRL in serum has led to a rapid increase of our knowledge of prolactin-physiology and -pathophysiology in men. hPRL is the only anterior pituitary hormone which is under predominantly inhibitory hypothalamic control. The effects of prolactin in the various species differ considerably, whereas in men it acts mainly upon the mammary gland and the gonadal system. Hyperprolactinemia leads typically to hypogonadism, amenorrhea and frequently galactorrhea. The hyperprolactinemia-hypogonadism-syndrome has been identified as a separate entity in recent years. Because of the relative frequency of this disease prolactin measurements have become of great importance in the diagnosis of sterility. Depending on the cause of hyperprolactinemia a neurosurgical, radiotherapeutical or medical treatment is indicated.
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