Thyroid Research Thyroid Research Archive Pregnancy

Thyroid function during pregnancy is normal in women with a history of hyperthyroidism caused by Graves’ disease who are in remission

(March 2006)

The background of the study. Hyperthyroidism caused by Graves’ disease is common in young women. Some have a long-term remission when treated with an antithyroid drug, and later they may become pregnant. In this study, thyroid function was evaluated in pregnant women with Graves’ hyperthyroidism who were in remission.

How the study was done. The study subjects were 34 pregnant women with a history of Graves’ hyperthyroidism in remission and 102 pregnant women with no history of thyroid disease. All the women with Graves’ hyperthyroidism had been treated with an antithyroid drug. When pregnant, none had a high serum thyrotropin (TSH)-receptor antibody value or was taking an antithyroid drug or thyroxine. Serum TSH, free thyroxine (T4), and free triiodothyronine (T3) were measured in all the women between 19 and 34 weeks of gestation.

The results of the study. The average gestational age of the women with a history of Graves’ hyperthyroidism was 27 weeks, as was that of the normal women. The mean serum TSH, free T4, and free T3 concentrations were similar in both groups (Table).

Table. Mean Serum TSH, Free T4, and Free T3 Concentrations during Pregnancy (19 to 34 Weeks’ Gestation) in Women with a History of Graves’ Hyperthyroidism and Normal Women.
	Serum TSH	Serum Free T4	Serum Free T3
	(mU/L)	(ng/dl)	(ng/dl)
Women with a history of Graves’ hyperthyroidism (n = 34)	1.1	0.96	0.26
Normal women (n = 102)	1.6	1.02	0.28
To convert serum free T4 and free T3 values to pmol/L, multiply by 12.9 and 15.4, respectively.

The conclusions of the study. Women who had hyperthyroidism caused by Graves’ disease and are in remission have normal thyroid function during pregnancy.

The original article. Luton D, Le Gac I, Noel M, Guibourdenche J, Polak M. Thyroid function during pregnancy in women with past Graves’ disease. BJOG 2005;112:1565-7.