Abstract

Background: Central hypothyroidism and autoimmune hyperthyroidism are contrasting pathologies requiring careful hormone monitoring for restoring euthyroidism. Their coexistence is rare and challenging for clinicians [1, 2].

Case Report: We have, herein, presented the case of a 41-year-old female patient with an unremarkable clinical history except for chronic autoimmune thyroiditis in euthyroidism. At the 21st week of gestation, she experienced a spontaneous abortion. The patient underwent an assessment of the uterine cavity, which was complicated by bleeding and hypotensive shock. In the postoperative course, the patient presented worsening headache, and after an MRI, the diagnosis of pituitary apoplexy due to an ischemic-hemorrhagic base was made. Laboratory tests showed anterior panhypopituitarism. Multiaxial replacement therapy was initiated with hydrocortisone, levothyroxine (LT4), and subsequently estrogen-progestin and GH. After two years of good recovery with stable LT4 dosage, the patient experienced palpitations and fine tremors; blood tests showed hyperthyroidism with suppressed Thyroid-stimulating Hormone (TSH) levels and elevated free thyroid fractions and anti-TSH receptor antibodies. Diagnosis of Graves’ disease was made, and therapy with methimazole was initiated. During antithyroid therapy, TSH remained persistently suppressed, consistent with the underlying central hypothyroidism. This condition required close follow-up, with monitoring based solely on free thyroid hormone levels. After six months of antithyroid therapy, disease remission was achieved, with negative antibodies and mild hypothyroxinemia. Therefore, methimazole was discontinued and replacement therapy gradually resumed until optimal hormone levels were reached.

Conclusion: This case is unique demonstrating autoimmune hyperthyroidism to coexist with central hypothyroidism, rendering TSH a misleading disease progression indicator. Consequently, managing Graves' disease has become more complex and challenging.