Missed Thyroid Diagnosis Due to Confusion Caused by Thyroxine Binding Protein Deficency, Hypo-TBG -emia.

40 Y/O F with a diagnosis of TBG deficency since age 16. She was noted by an endocrinologist, to have a small goiter then. No therapy was directed toward the goiter. Over the next 20+ years the patient was treated with thyroxine, T3, Triac,
Armour thyroid, and large amounts of iodine containing supplements. She had multiple CT scans with iodine contrast.The low Total T4 confused the physicians, into treating her for hypothyroidism. Her usual thyroid tests were compatible with low TBG.
The low Total T4, and normal TSH resulted in several CT scans of the head looking for a pituitary tumor. Iodine contrast dye for these tests resulted in iodine induced hyperthyroidism. However,there were other periods of hyperthyroidism caused by her large iodine intake. 2 years ago, a thyroid scan showed high iodine uptake and multiple hot nodules on scanning. There was multiple FNA biopsies of the 10 + nodules seen on ultrasound. They were all benign. She tried Wilson's Syndrome, an unproven, and dangerous T3 therapy Rxed by a physician, that put her in the emergency room with T3 induced rapid heart beats. Finally, she saw me for a consultation. She had a multinodular goiter with 4 autonomous hot nodules, on repeat thyroid scan, which were ripe for induction to hyperthyroidism with introduction of excess iodine. She had "normal" total T4 and suppressed TSH which in TBG deficiency, meant she was hyperthyroid. She is now off all thyroid preparations, and clean of supplement iodine, and is about to be treated with radioactive iodine to ablate the pre-toxic autonomous nodules in her goiter.

Key to case.

Hot nodules on seen on scan can be induced to over produce T4 when presented with excess iodine, and will surely become hyperthyroid if put on thyroid hormone.

Rare Low TBG is not a disease, and has no effects on the patient, but it can mask real disease, and in some cases cause unnecessary treatment for hypothyroidism.

Rare high TBG can cause the opposite effect. In 30 years I have stopped 2 patients from therapy for hyperthyroidism, who had excess TBG. They had high Total T4, a simple goiter, and were not toxic hyperthyroid.




Until the next thyroid rounds,

Dr.G.