How thyroid hormones (T3 & T4) is transferred?
Your hypothalamus releases thyrotropin-releasing hormone (TRH), which triggers your pituitary gland to release thyroid-stimulating hormone (TSH), which stimulates your thyroid to release T3 and T4.
Thyroid Profile Total, Thyroid Stimulating Hormone Total T3 Total T4, Serum Thyroid Profile