DIFFERENCES IN SERUM-LIPIDS, LIPOPROTEINS, SEX-HORMONE BINDING GLOBULIN AND TESTOSTERONE BETWEEN THE FOLLICULAR AND THE LUTEAL-PHASE OF THE MENSTRUAL-CYCLE

Fifty-four healthy women were studied during the follicular and the luteal phase of one menstrual cycle to determine possible cyclic influences on several parameters. After a 12-h overnight fast, blood samples were obtained between 08.00 h and 09.30 h and processed for total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apolipoproteins A-1 and B and total triglycerides. In the same samples we also measured serum concentrations of follicle-stimulating hormone, luteinizing hormone, 17beta-oestradiol, progesterone, sex hormone binding globulin and testosterone. Serum total cholesterol, low-density lipoprotein cholesterol and the related apolipoprotein B were decreased significantly with 0.35 mmol/l, 0.44 mmol/l and 15 mg/l. respectively, during the luteal phase as compared to the follicular phase (p less-than-or-equal-to 0.01). The ratios of low-density lipoprotein cholesterol/high-density lipoprotein cholesterol and of total cholesterol/high-density lipoprotein cholesterol were also significantly lower (p < 0.01) in the luteal phase because high-density lipoprotein cholesterol and its major carrier apolipoprotein A-1 as well as serum triglycerides remained unchanged in the two cycle phases compared. Sex hormone binding globulin was significantly higher (p < 0.001) in the luteal phase than in the follicular phase of the investigated cycles, whereas serum testosterone remained unchanged in the two cycle phases compared. Therefore, the free androgen index decreased in the luteal phase (p < 0.01). These results indicate the necessity to define the cycle phase in which blood has been collected during control cycles in studies concentrating on possible effects of oral contraceptives or other administered sex steroids on serum lipids, lipoproteins and androgen metabolism. Further, we suggest that variations in the serum concentrations of lipids and lipoproteins during the normal menstrual cycle should be considered when normal range values are defined.