Increased levothyroxine requirements presenting as "inappropriate" TSH secretion syndrome in a patient with nephrotic syndrome

Patients with primary thyroid failure on levothyroxine (LT4) replacement who develop nephrotic syndrome (NS) may rarely present with an increase in LT4 requirements. In this report, we describe a patient with thyroid failure following radioactive iodine ablation for Graves’ disease who required an escalation of LT4 doses following the onset of NS. The case presented with disproportionately elevated TSH levels in the presence of normal (or slightly subnormal) thyroid hormone levels, thus, masquerading as a state of “inappropriate” TSH secretion. This pattern of extreme dysregulation in thyroid function indices due to urinary loss of thyroid hormones has not been previously described in NS, and, therefore, extends the spectrum of endocrine manifestations of NS.