Endocrine Abstracts

Introduction: Graves’ and Hashimoto’s diseases are considered two extremes of the same autoimmune thyroid disease. Spontaneous conversion from hypothyroidism to hyperthyroidism is uncommon. On the other hand, Graves’ disease typically improves during pregnancy and worsens after delivery. We describe a patient with an unusual course of thyroid disease during pregnancy.

Case report: An 33-year-old woman, with a two-year history of hypothyroidism, treated with 75 μg of levothyroxine, presented in her 9th week of gestation with fatigue, sweating, palpitations and nervousness. Physical examination showed diffuse goitre, tachycardia (110 b.p.m) and distal tremor. Laboratory tests showed supressed TSH (<0.04; normal: 0.34–5 mU/l) and slightly increased free T₄ (1.66; normal: 0.6–1.6 pg/ml). Thyroid ultrasound showed global enlargement and an 8 mm hyperechoic nodule in the right thyroid lobe. Levothyroxine dose was halved and 2 weeks later, hyperthyroidism had worsened (TSH 0.01 mU/l, free T₄ 4.22 pg/ml, total T₃ 3.9 ng/ml and normal 1–2.2 ng/ml). TPO and TSI antibodies were positive. Levothyroxine was stopped and propylthiouracil (PTU) (daily dose 100 mg) was started and further increased and reduced again in the second trimester. In the third trimester of pregnancy, TSH was still supressed, but T₃ and free T₄ were in the normal range. Cesarean delivery was performed at 41 weeks, which resulted in the birth of a healthy girl. Anti-thyroid treatment was continued and radioiodine (7.5 mCi) was given 1 year after delivery, due to persistent hyperthyroidism. Two months later, the patient developed hypothyroidism (TSH 20.99 mU/l and free T₄ 0.15 pg/ml) and levothyroxine was resumed. Two years later, the patient is euthyroid on 50 μg of levothyroxine/day.

Discussion: Conversion of autoimmune hypo- to hyperthyroidism is exceptional during pregnancy. To our knowledge, there are only three cases previously reported. Routine and frequent assessment of thyroid function during pregnancy allows the diagnosis to be made assessment of thyroid function during pregnancy allows the diagnosis to be made. Levothyroxine dose was halved and two weeks later, hyperthyroidism had worsened (TSH 0.01 mU/l free T₄ 4.22 pg/ml, total T₃ 3.9 ng/ml and normal 1–2.2 ng/ml). TPO and TSI antibodies were positive. Levothyroxine was stopped and propylthiouracil (PTU) (daily dose 100 mg) was started and further increased and reduced again in the second trimester. In the third trimester of pregnancy, TSH was still supressed, but T₃ and free T₄ were in the normal range. Cesarean delivery was performed at 41 weeks, which resulted in the birth of a healthy girl. Anti-thyroid treatment was continued and radioiodine (7.5 mCi) was given one year after delivery, due to persistent hyperthyroidism. Two months later, the patient developed hypothyroidism (TSH 20.99 mU/l and free T₄ 0.15 pg/ml) and levothyroxine was resumed. Two years later, the patient is euthyroid on 50 μg of levothyroxine/day.