Thyroid Regulation
Underactive thyroid (hypothyroidism) is often overlooked or misdiagnosed and can be the underlying cause of these symptoms. Patients and their doctors often disregard these common signs of thyroid hormone deficiency, mistaking them for normal aging.1
Overactive thyroid (hyperthyroidism) afflicts fewer people than hypothyroidism, yet the symptoms can be equally devastating. Subclinical hyperthyroidism, characterized by suppressed thyroid stimulating hormone (TSH) levels accompanied by normal thyroid hormones (T4 and T3) levels,2 has been associated with increased rates of cardiovascular disease; arrhythmia in particular.3 Overt hyperthyroidism compromises bone health,4 elevates blood glucose levels,5 and often causes anxiety.6
In this protocol we will discuss the function and regulation of the thyroid gland, and the systemic implications of both hypothyroidism and hyperthyroidism. We will examine the importance of proper testing and interpretation of thyroid hormone levels and reveal natural approaches for maintaining optimal thyroid hormone levels.
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Thyroid Regulation
Role of the Thyroid
The thyroid is a butterfly-shaped organ located just below the Adam’s apple in the neck. Made up of small sacs, this gland is filled with an iodine-rich protein called thyroglobulin along with the thyroid hormones thyroxine (T4) and small amounts of triiodothyronine (T3).
In healthy individuals the gland is imperceptible to the touch. A visibly enlarged thyroid gland is referred to as a goiter. Historically, goiter was most frequently caused by a lack of dietary iodine.8 However, in countries where salt is iodized, goiter of iodine deficiency is rare.
Thyroid Regulation
Thyroid Regulation
The production of T4 and T3 in the thyroid gland is regulated by the hypothalamus and pituitary gland. To ensure stable levels of thyroid hormones, the hypothalamus monitors circulating thyroid hormone levels and responds to low levels by releasing thyrotropin-releasing hormone (TRH). This TRH then stimulates the pituitary to release thyroid stimulating hormone (TSH).9,10 When thyroid hormone levels increase, production of TSH decreases, which in turn slows the release of new hormone from the thyroid gland.
Cold temperatures can also increase TRH levels. This is thought to be an intrinsic mechanism that helps keep us warm in cold weather.11
Elevated levels of cortisol, as seen during stress and in conditions such as Cushing’s syndrome, lowers TRH, TSH and thyroid hormone levels as well.12,13
The thyroid gland needs iodine and the amino acid L-tyrosine to make T4 and T3. A diet deficient in iodine can limit how much T4 the thyroid gland can produce and lead to hypothyroidism.14
T3 is the biologically active form of thyroid hormone. The majority of T3 is produced in the peripheral tissues by conversion of T4 to T3 by a selenium-dependent enzyme. Various factors including nutrient deficiencies, drugs, and chemical toxicity may interfere with conversion of T4 to T3.15
Another related enzyme converts T4 to an inactive form of T3 called reverse T3 (rT3). Reverse T3 does not have thyroid hormone activity; instead it blocks the thyroid hormone receptors in the cell hindering action of regular T3.16
Ninety-nine percent of circulating thyroid hormones are bound to carrier proteins, rendering them metabolically inactive. The remaining “free” thyroid hormone, the majority of which is T3, binds to and activates thyroid hormone receptors, exerting biological activity.17 Very small changes in the amount of carrier proteins will affect the percentage of unbound hormones. Oral contraceptives, pregnancy, and conventional female hormone replacement therapy may increase thyroid carrier protein levels and, thereby, lower the amount of free thyroid hormone available.18 Read More Here ……..
Source: Thyroid Regulation Introduction | Life Entension
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