Development of Graves' Disease and the Recovery of TSH Secretion during a Long-term Follow-up of Isolated TSH Deficiency.

Isolated thyroid-stimulating hormone (TSH) deficiency is a rare form of central hypothyroidism that requires long-term levothyroxine replacement therapy. We report a rare case of isolated TSH deficiency in which Graves' disease developed after long-term thyroid hormone replacement therapy, followed by a recovery of the TSH secretory capacity. A 46-year-old woman with isolated TSH deficiency developed thyrotoxicosis with positive TSH receptor antibody levels and a preserved thyroid uptake on scintigraphy. After radioactive iodine therapy (131I, 13 mCi), her thyroid function stabilized, and a TRH stimulation test demonstrated a recovery of TSH secretion. This case suggests the potential plasticity of the hypothalamic-pituitary-thyroid axis.