Postpartum Thyroid Abnormalities and Systemic Lupus Erythematosus: Is There a Link?

Abstract Introduction: Postpartum Thyroiditis (PPT) is an autoimmune disorder characterized by destruction of the thyroid gland within the first year after delivery. Systemic Lupus Erythematosus (SLE), another autoimmune disease, has been associated with a spectrum of thyroid disorders. While the prevalence of thyroid diseases in patients with SLE is increased, the association between SLE and PPT is not well known. The infrequency of encountering SLE and PPT makes abnormal thyroid tests in the postpartum period a diagnostic challenge. Clinical Case: A 27-year-old G1P1001 who was five months postpartum and not breast feeding was referred to Endocrinology clinic for evaluation of abnormal thyroid function tests. Past medical history was significant for SLE with renal and pericardial involvement. SLE was well controlled, treated with hydroxychloroquine. Family history was significant for hypothyroidism in her mother. She was asymptomatic and appeared clinically euthyroid. Vitals were stable and physical exam was negative for goiter, nodule or orbitopathy. Lab results at two months postpartum showed an elevated TSH of 3.87 UIU/mL (Normal 0.40-3.8 UIU/mL) and at four months postpartum TSH was low at 0.012 UIU/mL. Repeat labs at five months postpartum continued to show a low TSH at 0.007 UIU/mL with mildly elevated Free T4 at 1.7 ng/dL (Normal 0.6-1.6 ng/dL) and elevated Free T3 of 6.0 pg/mL (Normal 2.1-3.8 pg/mL). Anti-thyroid peroxidase antibodies (TPO), thyroid stimulating antibodies (TSI) and TSH receptor antibodies (TRAb) were negative. Thyroid Ultrasound with Doppler was within normal limits. Radioactive Iodine Uptake and Scan, obtained at 6 months postpartum, showed high normal uptake (17% and 32% at 4 hours and 24 hours respectively), suggestive of recovery phase of PPT. The most recent TSH was elevated at 8.5 UIU/mL and Free T4 was low at 0.7 ng/dL. Disease course was consistent with PPT. Conclusion: The Th1 (T-helper) lymphocyte immune predominance in autoimmune thyroid disease and SLE is the immune-pathogenetic base of the association between both diseases. Postpartum thyroiditis is a variant of chronic autoimmune thyroiditis. Serum anti-TPO antibodies vary during pregnancy and tend to increase early and may decline later. Immunologic tolerance increases during pregnancy, fades in the postpartum period and makes interpretation of thyroid function tests and disease process challenging. Pregnant and postpartum patients who have SLE have increased prevalence of thyroid disease. Causes are multifactorial with a higher prevalence of hypothyroidism and thyroid autoantibodies. Hyperthyroidism is much less likely. One comparable study found 6 of 43 (14%) women with SLE developed PPT and only one of these patients had positive thyroid antibodies. These reports and our patient illustrate the variability of thyroid function tests in patients with SLE.