Current concepts of prolacting physiology in normal and abnormal conditions

Abstract

Currently the physiology and pathophysiology of pituitary prolactin secretion are under intensive investigation. Development of sensitive, specific radioimmunoassays for hPRL and improved roentgenographic techniques have increased the diagnostic acumen for incipient pituitary microadenomas. Several modalities of treatment are available at the present time which can result in improvement in the clinical symptoms of the amenorrheagalactorrhea syndromes. Eponymic classification of amenorrhea-galactorrhea syndromes should be discarded and appropriate diagnostic studies initiated to determine the etiology of the inappropriate breast secretion and/or elevated serum hPRL level.

PIP: This review assesses current knowledge of the control of human prolactin secretion, the means of altering it, and therapeutic regimens soon to reach the practitioner. Prolactin secretion appears to be under the control of hypothalamic neurotransmitter cells that stimulate pituitary lactotrophs via the hypothalamic-pituitary portal system, which is modulated by a prolactin-inhibiting factor and possibly a prolactin-releasing factor. Secretion is further modulated by estrogen and thyroid hormones at the pituitary level. Amenorrhea associated with hyperprolactinemia appears to be caused by hypothalamic dysfunction. In attempting to diagnose pituitary microadenomas as the cause of hyperprolactinemia, a thorough endocrine evaluation must be undertaken. Persons evidencing pituitary adenoma show a poor serum prolactin response to thyrotropin-releasing hormone in 70% of the cases, though false positives also occur. Bromergocryptine and 2-chloro-6-methyl-ergoline-8beta-acetonitrile methanesulfonate (Lergotrile, Lilly) have been used to sustain a reduced serum prolactin level, resulting in resumption of menses, ovulation, and pregnancy in patients without overt evidence of microadenoma. For those with adenoma, either surgical removal or radiation therapy is the conservative treatment.