Triphasic changes in thyroid function in a patient with primary hypothyroidism in the course of pregnancy and the early post-partum period.

We report a rare case of primary hypothyroidism in which thyroid function was changed from hypothyroidism to hyperthyroidism in the course of pregnancy and finally returned to hypothyroidism in the early post-partum period. She delivered an infant with neonatal Graves' thyrotoxicosis. Serum thyroid-stimulating antibodies (TSAb) and thyroid stimulating-blocking antibodies (TSBAb) coexisted in these patients. The triphasic changes in thyroid function may be explained by altered balance between TSAb and TSBAb in relation to pregnancy and delivery in the present case, although cellular immunity could be independently involved in atrophic changes in the postpartum period.