Both Graves disease and postpartum thyroiditis can cause hyperthyroidism in the postpartum period. A suppressed TSH with elevated total T4, FT4, and free triiodothyronine levels may be seen in both disorders. The presence of TPO antibodies with a low 4-hour RAIU is consistent with thyroiditis in this patient. The lack of exophthalmos, significant thyroid enlargement, and TSH receptor antibodies makes Graves disease unlikely in this case. Up to 50% of women who develop postpartum thyroiditis have high serum antibodies to TPO.2 Postpartum thyroiditis is an autoimmune-mediated inflammation of the thyroid gland that occurs in the first year after delivery. The mean prevalence of postpartum thyroiditis in iodine-sufficient areas is 5% to 7%.3 Considered to be a transient form of Hashimotos thyroiditis, postpartum thyroiditis occurs as the relatively immune-tolerant state of pregnancy normalizes after delivery. It occurs as either transient hyperthyroidism alone, transient hypothyroidism alone, or transient hyperthyroidism followed by transient hypothyroidism. Most women are euthyroid at 1-year postpartum. The most common presentation of postpartum thyroiditis is hypothyroidism without preceding hyperthyroidism, occurring in approximately 40% of patients. Approximately 20% to 30% of women with postpartum thyroiditis have hyperthyroidism alone. The remaining cases (25%) present with characteristic hyperthyroidism followed by hypothyroidism.2,4 The hyperthyroid phase of postpartum thyroiditis most commonly presents within 1 to 4 months of delivery and lasts from 2 to 8 weeks,2 whereas the hypothyroid phase occurs between 2 and 12 months postpartum and lasts from 2 weeks to several months.2,4 In Graves disease and TMG, RAIU would be elevated, not suppressed. Additionally, thyroid scan would reveal diffuse thyroid uptake with Graves disease and focal uptake with TMG. Infrequently, some women with postpartum thyroiditis will be TSH receptor antibody–positive. However, the prevalence of postpartum thyroiditis is 20 times that of Graves disease, making postpartum thyroiditis the more likely cause of hyperthyroidism in this population.5 Transient gestational hyperthyroidism can be seen in early pregnancy and occurs when high serum concentrations of human chorionic gonadotropin act as a weak stimulator of the TSH receptor.
- Postpartum thyroiditis.
2. Lazarus JH, Hall R, Othman S, et al. The clinical spectrum of postpartum thyroid disease. QJM 1996;89:429–35.
3. Muller AF, Drexhage HA, Berghout A. Postpartum thyroiditis and autoimmune thyroiditis in women of childbearing age: recent insights and consequences for antenatal and postnatal care. Endocr Rev 2001;22:605–30.
4. Stagnaro-Green A. Clinical review 152: postpartum thyroiditis. J Clin Endocrinol Metab 2002;87:4042–7.
5. Amino N, Tada H, Hidaka Y, et al. Therapeutic controversy: screening for postpartum thyroiditis. J Clin Endocrinol Metab 1999;84:1813–21.
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