Mechanical stimulation of the breast can increase prolactin and cause galactorrhea even if PRL is normal...
J Adolesc Health Care. 1984 Jul;5(3):210-2. Related Articles, Links
Benign galactorrhea/breast discharge in adolescent males probably due to breast self-manipulation.
Rohn RD.
Three adolescent males presented with nipple discharge. In two boys, the expressed secretion was clinically consistent with galactorrhea. Galactorrhea/breast discharge is a rare complaint in males of any age. Although galactorrhea is commonly associated with a neuroendocrine disorder or drug ingestion, the work-up in each, including basal prolactin level, was normal. Reluctantly, each by admitted to breast self-manipulation to reduce gynecomastia. When the behavior was discontinued, the galactorrhea/breast secretion ceased. Clinicians should be aware of this heretofore undescribed and apparently benign phenomenon. If basal hyperprolactinemia is absent in a male with a breast discharge and a history of breast manipulation, then an extensive work-up is not usually indicated.
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Klin Wochenschr. 1990 Dec 4;68(23):1157-67. Related Articles, Links
Control of prolactin secretion.
Benker G, Jaspers C, Hausler G, Reinwein D.
Abteilung fur Endokrinologie, Medizinische Klinik und Poliklinik, Universitat Essen.
1. Prolactin is a 21,500 Dalton single-chain polypeptide hormone but may occur in 50 kDa and 150 kDa molecular variants. 2. These large PRL variants may be secreted predominantly; this condition is termed "macroprolactinemia". It is characterized by high immunological and normal biological serum levels of prolactin, and lack of clinical symptoms of hyperprolactinemia. 3. The information on PRL is encoded on chromosome 6. Transcription can be enhanced and suppressed by a variety of hormonal factors. 4. PRL is secreted in a pulsatile fashion; it displays a circadian rhythm (with a maximum during sleep) and is stimulated by some amino acids. PRL also responds to mechanical stimulation of the breast. 5. PRL rises during pregnancy, and maintainance of hyperprolactinemia (and, thereby, physiological infertility) is dependent on the frequency and duration of breast feedings. 6. Hypothalamic regulation of prolactin mainly involves tonic inhibition via portal dopamine. The physiological importance of various stimulating factors present in the hypothalamus is still incompletely understood. In particular, there is still no place for TRH in PRL physiology. 7. PRL is released in response to stress; this response may be mediated by opioids. The low-estrogen, low-gonadotropin amenorrhea of endurance-training women is not mediated by prolactin, however. 8. Estrogens stimulate PRL gene transcription via at least two independent mechanisms. There are many clinical examples of this estrogen effect on prolactin serum levels, and also on the growth of prolactinomas. 9. Mild hyperprolactinemia remains an enigma which cannot satisfactorily be resolved by biochemical or radiological testing. The border between "normal" and "elevated" prolactin is ill-defined. The possibility of macroprolactinemia complicates this matter even further. 10. The number of drugs which suppress prolactin by acting on pituitary D2 receptors, and which are useful in the treatment of hyperprolactinemia, continues to increase. In the field of ergot alkaloids, parenteral application appears to be a logical solution to the problem of the high first-pass effect; in addition, this form of treatment is frequently better tolerated than the oral route. 11. Prolactinoma development is presently being studied employing molecular biological techniques; the question of whether tumorigenesis can be attributed to specific defects of gene regulation remains to be answered.