BACKGROUND

While it is recognized that patients sometimes recover from autoimmune hypothyroidism, little is known about how rapidly this may occur.

CASE REPORTS

Two 13 year old girls had severe primary hypothyroidism (total T4 14.2 nmol/L with TSH 468 miU/L and total T4 7.7 nmol/L with TSH 183 miU/L) accompanied by goiter and positive thyroid peroxidase antibodies. There were delays in starting thyroid hormone replacement, and complete reversal of hypothyroidism was documented within 2 months in both cases. One of the girls had recurrence of severe hypothyroidism after being euthyroid for 18 months.

REVIEW OF LITERATURE

There are few published studies which have looked systematically at reversibility of acquired hypothyroidism, but one Japanese study found that recovery from autoimmune hypothyroidism may occur within weeks. Other causes of primary hypothyroidism (TSH-blocking antibodies, iodine excess, medications) seem less likely, so this probably represents rapid spontaneous reversal of autoimmune hypothyroidism.

CONCLUSION

Patients with severe autoimmune hypothyroidism may have spontaneous normalization of thyroid tests within weeks to months after diagnosis. This suggests that reevaluating the need for thyroid hormone replacement in selected patients with persistently normal TSH during therapy should be considered.