Perimenopause can last anywhere from one to 10 years. During this time, the ovaries function erratically and hormonal fluctuations may bring about a range of changes, including hot flashes, night sweats, sleep disturbances, and heavy menstrual bleeding.
The thyroid hormones, triiodothyronine (T3) and its prohormone, thyroxine (T4), are tyrosine-based hormones produced by the thyroid gland that are primarily responsible for regulation of metabolism. Iodine is necessary for the production of T 3 and T 4.hyroxine is produced by attaching iodine atoms to the ring structures of tyrosine molecules. Thyroxine (T 4) contains four iodine atoms. Triiodothyronine (T 3) is identical to T 4, but it has one less iodine atom per molecule. Iodide is actively absorbed from the bloodstream by a process called iodide trapping.
For example, thyrotropin-releasing hormone (TRH) is released from the hypothalamus in response to low levels of secretion of thyroid-stimulating hormone (TSH) from the pituitary gland. The TSH in turn is under feedback control by the thyroid hormones T4 and T3.