Ovarian function is effectively inhibited by a low-dose triphasic oral contraceptive containing ethinylestradiol and levonorgestrel.

For various metabolic and clinical reasons, it has been strongly advocated to reduce the dose of both the estrogen and progestogen components of oral contraceptives (OCs). In this study, we compared after 6 months of treatment, the action on various hormonal parameters of a standard-dose combined OC containing ethinylestradiol (EE) 0.050 mg and levonorgestrel (LNg) 0.250 mg and a low-dose triphasic combination containing a 59% reduced amount of the same steroids. Hormonal measurements in the last 3 days of OC intake indicated that basal levels of FSH and LH were less inhibited by the low-dose preparation, while PRL levels were unchanged. However, gonadal function was effectively inhibited by both high and low dose OCs, as demonstrated by equally low levels of E2, E1, P and 17-P. Consequently, no residual gonadal function could be anticipated from the observed low steroid concentrations. These results corroborated other studies (reviewed in this paper) in which serial hormonal measurements also revealed a complete lack of follicular maturation during low-dose triphasic OC treatment. Moreover, inhibition of circulating levels of A, DHEA, DHEAS, free T and DHT was similarly obtained with both preparations. Collectively, these data indicate that ovarian function is as effectively inhibited by a low-dose triphasic preparation as by a higher, standard-dose OC containing the same steroids.