The effect of combined oral contraceptives on thyrotoxicosis.

ABSTRACT

The influence of combined oral contraceptives, namely, ethinyl estradiol (30 µg) and levonorgestrel (150 µg) was studied in nine cases of thyrotoxicosis divided into two groups one group of htyrotoxic woman treated with propyl thiouracil (PTU) and another untreated group. The latter group of patients were than maintained on both PTU and the combined oral contraceptive pills; some cases were studied for 16-33 months. Before, during and after treatment, all patients were tested and confirmed by clinical examinations and thyroid function tests which were divided into two group in vivo (24h 131/I uptake and T3-suppression test) and in vivo (total serum thyroxine (TT4), total T3 (TT3), T3 uptake (T3U), free thyroxine index (FTI) and thyrotropin (TSH). The results revealed that the values of TT4, TT3 and FTI were markedly high in the untreated group but these values decreased significantly (P<0.001) and remained within normal ranges after treatment with PTU and the contraceptive pills was initiated. Improved clinical symptoms and sings were also observed. However, the levels of TT4, TT3 and T3 uptake were elevated in the long-term treatments of both groups, but the FTI and TSH values were within normal limits, indicating that the values of FTI as well as TSH gave effective measurements of thyroid activity in evaluating the patients whose total thyroid hormones were abnormal because of altered TBG concentration and binding capacity. Therefore, our finding suggested that the prolonged use of combined oral contraceptive pills dose not interfere with medical treatment of thyrotoxic patients.