Lynestrenol induced therapeutic amenorrhea: effects of dose reduction on serum sex-hormones and lipids.

The effect of reducing the dose of peroral lynestrenol by half on serum sex-hormone, lipid and lipoprotein status was studied in 21 mentally retarded women with therapeutic amenorrhea (TA). They had previously received 5 or 10 mg peroral lynestrenol daily for periods ranging from 32 to 196 months. Dose halving of lynestrenol resulted in an increase in serum total testosterone (T) by 16% (p less than 0.05), sex-hormone binding globulin (SHBG) by 39% (p less than 0.01) and high-density lipoprotein cholesterol (HDL-C) by 28% (p less than 0.001). Both the mean serum total and free concentrations of norethisterone (NET and fNET) decreased by 60% (p less than 0.001). The serum concentrations of 17-beta-estradiol (E2), its free fractions (fE2) and free T (fT) were not significantly altered. Significant correlations were observed between the change in HDL-C and the change in T (r = 0.45, p less than 0.05), between the change in SHBG and the change in T (r = 0.62, p less than 0.01), fT (r = 0.43, p less than 0.05) and E2 (r = 0.51, p less than 0.05). The elevation of HDL-C was probably caused by the reduced serum NET concentrations. This also resulted in an increase in serum SHBG concentration, which is regarded as an indicator of the overall estrogen/androgen ratio.