Abnormal circulating thyroid hormone concentration

What it means

Any deviation from the normal range of the hormones produced by the thyroid gland.

Thyroid hormones (TH) are involved in the regulation of metabolism, proliferation, and growth of most tissues. Serum TH levels are tightly controlled by the hypothalamic, pituitary, and thyroid (HPT) axis to deliver appropriate amounts of TH to target tissues. The two major THs (T3 and T4) are iodothyrosines synthesized by the thyroid gland under the control of thyrotropin/thyroid stimulating hormone (TSH), a glycoprotein heterodimer that is produced by the pituitary gland. TSH, in turn, is regulated by thyrotropin releasing hormone (TRH), a tripeptide generated by the hypothalamus that is released into its own portal system to reach the pituitary. Both the production of TRH and TSH are under negative feedback control determined by the circulating free TH concentrations.

Rare diseases that can present with this1

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Abnormal thyroid hormone level