RELATIONSHIP BETWEEN SERUM PROLACTIN LEVELS AND PROTEIN-COMPOSITION OF BREAST SECRETIONS IN NONLACTATING WOMEN

The potential relationship between serum PRL levels and protein compos ition of breast secretions was evaluated in 54 premenopausal nonlactat ing women during the luteal phase of their menstrual cycle. Women were classified into four groups according to the presence or absence of b reast pathology and to the protein pattern of their breast secretions. Type I mammary fluids contain Zn-alpha(2)-glycoprotein, apolipoprotei n D, and gross cystic disease fluid protein-15, whereas Type II fluids are characterized by the presence of some milk proteins such as lacto ferrin, lysozyme, and Lu-lactalbumin. Basal serum levels of PRL, as we ll as of progesterone, LH, FSH, TSH, T-3, and T-4 were within normal r ange, and no significant differences were found between the different groups of women under study. However, after a TRH stimulation test, th e maximum PRL response was significantly higher (P < 0.02) in normal w omen with Type II secretions than in those with Type I (64 +/- 6.8 mu g/L us. 43.7 +/- 3.9 mu g/L). Similarly, when PRL concentrations in pa tients with benign breast disease were considered, those with breast f luids containing milk proteins had a rise in PRL secretion after TRH s timulation significantly higher (P < 0.05) than those with fluids lack ing these proteins (77.1 +/- 6.2 vs. 58.8 +/- 5.1 mu g/L). These resul ts indicate that the occurrence of milk proteins in breast secretions from nonlactating women is associated with an increase in serum PRL co ncentrations after TRH stimulation, and opens the possibility of using breast fluid protein analysis as a simple and noninvasive procedure f or studies on the putative role of PRL in the development of benign an d malignant breast diseases.