HYPERSECRETION (contd) Prolactin
This hormone helps to promote lactation. The introduction of immunoassay techniques has shown prolactinomas to be the commonest type of pituitary tumour and aided early detection of prolactin microadenomas. Female: Male ratio - 4:1 This tumour may present with
In males, the tumour may present with IMPOTENCE or remain undetected until local pressure effects occur.
In most centres, a serum prolactin of 360 mU/1 is considered abnormal, but before assuming the presence of a prolactin secreting tumour, other causes must be excluded.
Causes of hyperprolactinaemia
- Pregnancy Since thyrotropic hormone
- Drugs (phenothiazines, oestrogens) (TRH) stimulates prolactin release, prolactin
- Hypothyroidism levels are high in primary hyperthyroidism.
- Renal disease
- Pituitary adenoma
- Hypothalamic lesion (e.g. sarcoid, craniopharyngioma) or the pituitary stalk syndrome
Prolactin differs from other anterior pituitary hormones in that it is under tonic inhibitory control from the hypothalamus. Hypothalamic lesions or raised intrasellar pressure, compromising hypothalamic-pituitary perfusion (i.e. the 'pituitary stalk syndrome') produce a rise in serum prolactin, but levels seldom exceed 2000 mU/1. Prolactin levels above 4000 mU/1 invariably indicate prolactinoma.
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