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.
During the menstrual cycle, when an egg is released from the ovary at ovulation (approximately day 14), the remnants of the ovarian follicle that enclosed the developing egg form a structure called the corpus luteum. This releases progesterone and, to a lesser extent, oestradiol. The progesterone prepares the body for pregnancy in the event that the released egg is fertilised. If the egg is not fertilised, the corpus luteum breaks down, the production of progesterone falls and a new menstrual cycle begins.