Physiopathology of prolactin secretion in obesity.

In many species prolactin is of biological importance and has a major role in determining the deposition and mobilization of fat. In human physiology, outside pregnancy, prolactin secretion is altered by increasing body weight in both children and adults. Prolactin in this circumstance appears to be marker of hypothalamic-pituitary function: the prolactin response to insulin-hypoglycaemia, thyrotrophin releasing hormone stimulation and other stimulatory factors may be diminished. In addition, obesity alters the 24h spontaneous release of prolactin with a generalised dampening of release. A number of explanations have been given as possible causes for these alterations, but it seems likely that they reflect obesity per se and are associated with hyperinsulinaemia. Weight reduction, with accompanying decrease in plasma insulin levels, leads to a normalization of prolactin responses in most, but not all, circumstances. To date, no molecular basis has been identified which links prolactin with increasing body fatness, weight and appetite: new data suggests a possible link in obese men between fasting plasma prolactin and leptin concentrations.