Effect of danazol on thyroid function in women

A longitudinal study of thyroid function during danazol treatment was performed in 18 women. Serum concentrations of thyroid stimulating hormone (TSH), thyroxine (T4), tri-iodothyronine (T3), free T4-and free T3 index as well as thyroid hormone binding globulin (TBG) were measured before and during 6 months therapy. Thyroxine binding globulin showed a marked decrease to one third of the pretreatment level. All the hormones showed significant alterations within the normal ranges for this group. T3 and T4 decreased slightly and the free T4 and free T3 index showed an increase. TSH decreased from 2.4 +/- 0.6 to 1.7 +/- 0.3 mIU/l. The observed hormonal changes were most likely induced by the decreased TBG concentrations and were probably without pathological significance. However these changes must be kept in mind when thyroid function tests from patients with danazol are evaluated.