Abstract
Familial dysalbuminemic hyperthyroxinemia (FDH) is a form of euthyroid hyperthyroxinemia caused by ALB gene variants that is commonly misdiagnosed in clinical practice. When coexisting with papillary thyroid carcinoma (PTC), this condition may complicate postoperative management strategies. This study aims to enhance clinical recognition of the coexistence of FDH and PTC and explore evidence-based management approaches. We retrospectively analyzed the diagnostic and therapeutic course of a patient with concurrent FDH and PTC in our clinic and reviewed the current literature. The proband exhibited unsuppressed thyrotropin (TSH) by levothyroxine (L-T4) monotherapy after PTC surgery, with abnormal, persistently elevated total thyroxine (T4) and free T4 levels. Further review of the medical records revealed a similar pattern of thyroid function abnormalities preoperatively. Genetic testing confirmed FDH caused by an ALB gene c.725G>A mutation. Sanger verification confirmed that both the proband's mother and daughter carried the same variant. The proband ultimately achieved adequate TSH suppression with the combination therapy of L-T4 and desiccated thyroid extract (DTE). This case highlights the importance of considering FDH when postoperative T4 and TSH levels show discordance in PTC patients. Increased albumin-T4 binding affinity in these patients may prevent adequate TSH suppression with L-T4 monotherapy, while DTE directly delivers triiodothyronine, without requiring peripheral conversion. Therefore, combination therapy with L-T4 and DTE may achieve effective TSH suppression in these patients.