How to manage hypothyroid disease in pregnancy
Pregnancy complicated by hypothyroidism puts mother and fetus at risk—symptoms or otherwise
Managing hypothyroidism in pregnancy
The treatment of choice for correction of hypothyroidism is synthetic T4, or levothyroxine (Levothyroid, Levoxyl, Synthroid, and Unithroid). Initial treatment in the nonpregnant patient is 1.7 μg/kg/day or 12.5 to 25 μg/day adjusted by 25 μg/day every 2 to 4 weeks until a euthyroid state is achieved.13
Patients who were on thyroxine therapy before pregnancy should increase the dose by 30% once pregnancy is confirmed.1,5 Serum thyrotropin levels should be monitored every 4 weeks to maintain a TSH level between 1 and 2 mU/L and FT4 in upper third of normal.1 Once a euthyroid state has been achieved, thyrotropin levels should be monitored every trimester until delivery. FIGURE 2 provides an algorithm for management of hypothyroidism in pregnancy.
FIGURE 2 During pregnancy, thyroid function merits regular monitoring, fine-tuning of treatment
Postpartum thyroiditis
About 5% of all obstetrical patients develop postpartum thyroiditis. Approximately 45% of these women present with hypothyroidism, with the rest evenly divided between thyrotoxicosis (hyperthyroidism) and thyrotoxicosis followed by hypothyroidism. Unfortunately, the signs and symptoms of hypo- and hyperthyroidism are similar to the postpartum state. Many of these patients are not diagnosed. A high index of suspicion warrants thyroid function testing. Women who have a history of type 1 diabetes mellitus have a 25% chance of developing postpartum thyroid dysfunction.
The diagnosis is made by documenting abnormal levels of TSH and FT4. Postpartum hyperthyroidism may be diagnosed by the presence of antimicrosomal or thyroperoxidase antithyroid peroxidase antibodies. Goiter may be present in up to 50% of patients.
Postpartum thyroiditis has two phases
The first phase, also known as the thyrotoxic phase, occurs 1 to 4 months after delivery when transient thyrotoxicosis develops from excessive release of thyroid hormones. The most common symptoms with early postpartum thyroiditis are fatigue and palpitations. Approximately 67% of these women will return to a euthyroid state, and thioamide therapy is generally considered ineffective. Hypothyroidism can develop within 1 month of the onset of thyroiditis.
The second phase occurs between 4 and 8 months postpartum, and these women present with hypothyroidism. Thyromegaly and associated symptoms are common. Unlike the first (thyrotoxic) phase, medical treatment is recommended. Thyroxine treatment should be initiated and maintained for 6 to 12 months. Postpartum thyroiditis carries a 30% risk of recurrence.14
Postpartum thyroiditis may be associated with depression or aggravate symptoms of depression, although the data on this association are conflicting. The largest study addressing this issue concluded that there was no difference in the clinical and psychiatric signs and symptoms between postpartum thyroiditis and controls.15 Nevertheless, it would seem prudent to evaluate thyroid function in postpartum depression if other signs of thyroid dysfunction are present.
