methimazole and Puerperal-Disorders

For many years, breast-feeding was forbidden if methimazole (MMI) was being used. However, a few studies have demonstrated the relative safety of MMI. The purpose of this study was to evaluate thyroid function of breast-fed infants whose lactating mothers became hypothyroid while taking methimazole. Between 1990 and 2001, 134 thyrotoxic lactating mothers received MMI while breast-feeding. MMI therapy was initiated between 2-8 months postpartum, 10-30 mg for the first month and 5-10 mg from the second until the twelfth month. In 16 mothers, TSH was increased at the end of one month of MMI therapy (Group 1). Infants of 18 mothers whose serum TSH was normal at the end of the first month were included as controls (Group 2). Mothers and their infants were clinically evaluated and serum T4, T3 and TSH were measured before and at 1, 2, 4, 8 and 12 months after MMI therapy. Serum MMI was measured in 8 infants 2 h after breast-feeding. Mean +/- SD of FT4I and FT3I were not statistically different between the two groups of mothers before MMI therapy. In all 34 mothers thyroid indices decreased one month after MMI therapy; FT4I: Group 1 from 19.8 +/- 4.3 to 6.0 +/- 4.8 (p<0.001) and Group 2 from 20.3 +/- 4.7 to 11.4 +/- 4.1 (p<0.001); FT3I: Group 1 from 602 +/- 56 to 146 +/- 52 (p<0.001) and Group 2 from 562 +/- 42 to 186 +/- 39 (p<0.001). The difference in FT4I, FT3I and TSH (20 +/- 18 vs 2.1 +/- 1.1 mU/l, p<0.001) between the 2 groups was significant at the end of the first month of MMI therapy. There was no significant difference in thyroid function of infants of these two groups one month after MMI therapy and all tests remained within the normal range during 12 months of treatment of their lactating mothers. Serum MMI levels were less than 0.03 in 6 and 0.03 and 0.035 microg/ml in the other 2 infants. The results further indicate the safety of MMI therapy in breast-feeding thyrotoxic women.

Topics: Adult; Antithyroid Agents; Breast Feeding; Chi-Square Distribution; Contraindications; Female; Follow-Up Studies; Humans; Hypothyroidism; Infant; Lactation; Methimazole; Milk, Human; Puerperal Disorders; Retrospective Studies; Thyroid Function Tests; Thyroid Gland; Thyrotoxicosis; Thyrotropin; Thyroxine; Triiodothyronine

Topics: Adult; Antithyroid Agents; Female; Graves Disease; Humans; Hypothyroidism; Iodine Radioisotopes; Methimazole; Pregnancy; Puerperal Disorders; Thyroiditis, Autoimmune; Thyroxine

Thyrotoxicosis occurs more frequently during the post-partum period than at other times in women of childbearing age. Graves' disease and post-partum thyroiditis are two major causes of thyrotoxicosis in this period. The major task lies in differentiation of these two diseases in the post-partum period; since throtoxicosis caused by post-partum thyroiditis usually does not require treatment. The radioiodine uptake is elevated or normal in Graves' disease and low in post-partum thyroiditis, and TSH-receptor antibodies are positive in Graves' and negative in post-partum thyroiditis. Post-partum thyrotoxicosis due to Graves' disease may be treated with radioiodine but it requires radiation safety measurements for infant and is contraindicated if the mother is breast-feeding. Antithyroid drugs are the mainstay of the treatment of post-partum thyrotoxicosis. Recent investigations conclude that neither propylthiouracil nor methimazole cause any alterations in thyroid function and physical and mental development of infants breast-fed by lactating thyrotoxic mothers, and both can be safely administered in moderately high doses during lactation.

Topics: Antithyroid Agents; Breast Feeding; Female; Graves Disease; Humans; Infant, Newborn; Iodine Radioisotopes; Methimazole; Propylthiouracil; Puerperal Disorders; Radiotherapy; Thyroidectomy; Thyroiditis; Thyrotoxicosis; Thyrotropin; Thyroxine; Triiodothyronine

A 28-year-old woman with thyroid hemiagenesis, who had been diagnosed as having Graves' disease, became pregnant during the course of methimazole treatment. The treatment was terminated in the second trimester. She delivered a normal infant at full term. She became thyrotoxic 3 months after the delivery, hypothyroid 6 months after the delivery, and finally euthyroid 11 months after the delivery without undergoing any treatment. This clinical course indicates that she developed silent thyroiditis after the delivery. A diagnosis of thyroid hemiagenesis was made on the basis of ultrasonography of the thyroid and 99mTc-pertechnetate thyroid scintiscan.

Topics: Adult; Antithyroid Agents; Female; Graves Disease; Humans; Hypothyroidism; Methimazole; Pregnancy; Pregnancy Complications; Puerperal Disorders; Thyroid Gland; Thyroiditis

In 35 infants of lactating mothers with thyrotoxicosis who were receiving 5 to 20 mg methimazole daily, serum levels of thyroxine, triiodothyronine, thyrotropin were within normal ranges 1 month after the start of breast-feeding. Thyroid function in breast-feeding infants of six lactating mothers receiving methimazole, 20 mg for the first, 10 mg for the second, and 5 mg for an additional 4 months, remained normal. These results suggest the safety of methimazole therapy in lactating mothers.

Topics: Adult; Antithyroid Agents; Breast Feeding; Dose-Response Relationship, Drug; Drug Administration Schedule; Female; Follow-Up Studies; Humans; Infant; Infant, Newborn; Male; Methimazole; Pregnancy; Pregnancy Complications; Puerperal Disorders; Thyroid Function Tests; Thyrotoxicosis; Thyrotropin; Thyroxine; Triiodothyronine