I haven't completely digested
this yet, but I think it may be significant information for me:
The amount of thyroid hormone manufactured by the thyroid gland is primarily governed by the pituitary gland, which produces TSH. The amount of TSH delivered to the thyroid gland tells the thyroid how much thyroid hormone to manufacture. T4 is the main thyroid hormone produced by the thyroid. A well regulated process causes T4 to lose iodine, generating the much more potent thyroid hormone T3. The amount of T3 present in the brain must remain within optimal range to keep the body functioning properly and is crucial for maintaining physical and mental health. Thyroid peroxidase, TPO, is an enzyme that aids the synthesis of thyroid hormone. In 90% of patients with Hashimoto's there is the presence of high levels of these antibodies. Individuals with other autoimmune disorders often have high TPO levels, as do women with polycysctic ovaries. Since early identification of antibodies can result in treatment to improve patient health and well being, testing TPO in those with sub-clinical hypothyroidism can be beneficial. Thyroid imbalance not only effects body weight, but also mood, emotions, behavior, sex life, menstrual problems, infertility, depression and anxiety disorders.
The thyroid gland produces two hormones: T4 (80%) and T3 (20%). Each thyroid hormone is made up of a tyrosine (protein) surrounded by four (T4) and three (T3) iodines. T4 is the "inactive," while T3 is the "active" component. Thyroid hormones set metabolic activity and are thus responsible for the speed at which every enzyme action in the body takes place. When the thyroid gland produces T4, it is taken up by every cell in the body, and converted into T3 which produces activity within the cell. When thyroid hormones are transported in the blood they are "bound" to a protein, Thyroid Binding Globulin (TBG), that temporarily holds them inactive. This protein may be manipulated by many illnesses and medication. Therefore, the measurement of the unbound, "free" levels of T3 and T4 thyroid hormones as conducted in blood spot testing at ZRT Laboratory is the most accurate.
Functional Thyroid Deficiency when free T3, free T4 and TSH are within normal range but symptoms (particularly a low basal temperature) are consistent with a hypothyroid state, a functional thyroid deficiency may exist. In this case, adequate thyroid is present but the tissues fail to respond. This functional thyroid deficiency or "thyroid resistance" is often caused by autoimmune thyroiditis (Hashimoto's) which can be identified using Thyroid Peroxidase Antibody - TPO testing. Other causes of functional thyroid deficiency are estrogen dominance (excessive estrogens in the absence of adequate progesterone), low anabolic steroids (testosterone and DHEAS), and/or adrenal imbalance (low or high cortisol). If thyroid resistance is suspected (i.e. thyroid tests are normal but sumptoms indicate hypothyroidism), salilva testing for stradiol, progesterone, testosterone, DHEAS and am/pm cortisol is strongly recommended.
More
information on the function of T4 in relation to TSH:
If the T4 level is low and TSH is not elevated, the pituitary gland is more likely to be the cause for the hypothyroidism. Of course, this would drastically effect the treatment since the
pituitary gland also regulates the body's other glands (adrenals, ovaries, and testicles) as well as controlling growth in children and normal kidney function. Pituitary gland failure means that the other glands may also be failing and other treatment than just thyroid may be necessary. The most common cause for the pituitary gland failure is a tumor of the pituitary and this might also require surgery to remove.