The thyroid is a bilobed gland butterfly shaped placed in the neck, in front of the proximal trachea. The left and right lobes extend along either side of the trachea and larynx close to the carotid arteries.
The hypothalamus stimulates the pituitary gland through thyrotropin-releasing hormone (TRH) to secrete the pituitary hormone thyrotropin (TSH) that is released to the blood and stimulates the thyroid follicular cells. These cells release thyroxine or T4, which is the inactive hormone that is converted to active thyroid hormone T3. Clinically thyroid function is evaluated though free thyroxine T4 and TSH levels.
Thyroid hormone increases cell metabolism and is involved in basal metabolic rate, cardiac and respiratory rate, fetal development, nervous system stimulation, reproductive health, and other endocrine organ functions.
Twin and family studies suggest that thyroid function is highly heritable, up to 65%. To date, several GWAS and meta-analysis found more than 15 loci related to thyroid function.
Gene or region studied