Insulin sensitivity and lipid profile in prolactinoma patients before and after normalization of prolactin by dopamine agonist therapy

Hyperprolactinemia has been associated with impaired metabolism, including insulin resistance. However, the metabolic effects of elevated prolactin (PRL) levels are not completely clarified. The aim of this study was to obtain more insights of metabolic consequences in hyperprolactinemia patients. Fourteen consecutive patients, eight women and six men, aged 39.7 (+/- 13.7) years with prolactinomas (median PRL 72 [49-131] mu g/L in women and 1,260 [123-9,600] mu g/L in men) were included. Anthropometric data and metabolic values were studied before and after 2 and 6 months on DA agonists (Bromocriptine [5.7 (+/- 3.9) mg/day, n = 13] or Cabergoline [0.5 mg/week, n = 1]). Euglycemic hyperinsulinemic clamps were studied in six patients before and after 6 months of treatment. PRL normalized in all patients. Anthropometric data changed only in males with a significant decrease of median body weight (95.6 [80.7-110.1] to 83.4 [77.8-99.1] kg, P = 0.046), waist circumference and fat percentage after 6 months. LDL cholesterol was positively correlated to PRL at diagnosis (r = 0.62, P = 0.025) and decreased within 2 months (3.4 [+/- 0.9] to 2.9 [+/- 0.6] mmol/L, P = 0.003). Insulin, IGFBP-1 and total adiponectin levels did not change. Insulin sensitivity tended to improve after 6 months; M-value from 5.7 (+/- 1.8) to 7.8 (+/- 2.6) mg/kg/min, P = 0.083 and per cent improvement in M-value was correlated to per cent reduction in PRL levels (r = -0.85, P = 0.034). In conclusion, beneficial metabolic changes were seen in prolactinoma patients after treatment with DA agonists, underscoring the importance of an active treatment approach and to consider the metabolic profile in the clinical management of hyperprolactinemia patients.