Endocrine Abstracts

Objective: Platelet activation is a recently recognized characteristic of prolactin, which functions through the potentiation of ADP-induced P-selectin expression on platelets. Studies in hyperprolactinemic patients demonstrated atherosclerotic disorders related to insulin resistance; convenient milieus for platelet activation. To investigate the association between hyperprolactinemia and platelet activation related to P-selectin expression, we studied on hyperprolactinemic and normoprolactinemic patients.

Method: After exclusion of any factor that might interfere with platelet functions, 32 naïve hyperprolactinemic and 33 age-body mass index-matched normoprolactinemic, non-smoking premenopausal women were included; 30.6±8 vs 29.8±7.7 years, 26.8±5.4 vs 24.8±5.2 kg/m², prolactin 1889.8±886 vs 335.9±117.9 mU/lt. Measurements regarding insulin sensitivity; waist circumference, blood pressure, fasting plasma glucose, insulin and lipids were also matched. The flow-cytometry method was used to determine the ADP stimulated P-selectin expression of the platelets. Serum prolactin was measured before and after polyethylene glycol precipitation (PEG) in hyperprolactinemic group. The diagnosis of macroprolactinemia was regarded as certain if the prolactin recovery in a serum was <40%.

Results: The ADP stimulated P-selectin expression of the platelets was higher in hyperprolactinemic group; 14.2±15.5% vs 6.7±5.2%, (P=0.01). The frequency of macroprolactinemia was found to be 29%. There was a significant correlation between prolactin levels and ADP stimulated P-selectin expression before PEG (r=0.3, P<0.02). The ADP stimulated P-selectin expression rates were similar between macroprolactin negative (true hyperprolactinemia) (n=21) and macroprolactin positive (n=11) subgroups; 13.6±16.4% vs 15.3±14.4% (P=0.7). It kept being higher than the controls in both subgroups; 13.6±16.4%, (P=0.03) and 15.3±14.4%, (P=0.005), respectively.

Conclusion: Platelet activation is involved in the pathogenesis of atherosclerotic disorders related to insulin resistance. In this study, performed on completely matched group of cases regarding insulin sensitivity markers, hyperprolactinemia itself has been detected to bring an increased risk for platelet activation. It has also been clearly demonstrated that macroprolactinemia may cause platelet aggregation just as true hyperprolactinemia.