thyroid hormone


Also found in: Dictionary, Thesaurus, Acronyms, Encyclopedia, Wikipedia.

thyroid hormone

n.
A hormone, especially thyroxine or triiodothyronine, produced by the thyroid gland.

thyroid hormone

an iodine-containing compound secreted by the thyroid gland, predominantly as thyroxine (T4) and, in smaller amounts but four times more potent, triiodothyronine (T3). These hormones increase the rate of metabolism; affect body temperature; regulate protein, fat, and carbohydrate catabolism in all cells; maintain growth hormone secretion, skeletal maturation, and the cardiac rate, force, and output; promote central nervous system development; stimulate the synthesis of many enzymes; and are necessary for muscle tone and vigor. Derivatives of thyronine, T4 and T3, are synthesized in the thyroid gland by a complex process involving the uptake, oxidation, and incorporation of iodide and the production of thyroglobulin, the form in which the hormones apparently are stored in thyroid follicular colloid. After the proteolysis of thyroglobulin, T4 and T3 are released and transported in the blood in strong, but noncovalent, association with certain plasma proteins; T4 accounts for approximately 90% of iodine in circulation, and T3 for 5%. All phases of the production and release of T4 and T3 are regulated by the thyroid-stimulating hormone secreted by the anterior pituitary gland. Production of thyroid hormones is excessive in Graves' disease and toxic nodular goiter (Plummer's disease), diminished in myxedema, and absent in cretinism. The normal 6- to 7-day half-life of T4 in blood is reduced to 3 or 4 days in hyperthyroidism and extended to 9 or 10 days in myxedema. T3 has a normal half-life of 2 days or less and, like T4, is metabolized most actively in the liver. Pharmaceutic preparations of thyroid hormones extracted from animal glands and the synthetic compounds levothyroxine sodium and liothyronine sodium are used as replacement therapy in patients with hypothyroidism. The dosage is initially low and is gradually increased to the optimal level based on the patient's clinical response and tests of the findings on thyroid function studies. Overdosage or a rapid increase in the dosage may result in signs of hyperthyroidism, such as nervousness, tremor, tachycardia, cardiac arrhythmia, and menstrual irregularity.

thyroid hormone

Either of two hormones, thyroxine (T4) or triiodothyronine (T3, secreted by the follicles of the thyroid gland. They act on receptors in tissues throughout the body to increase the production of cellular proteins, the metabolic rate, and the activities of the sympathetic nervous system. Deficiency of thyroid hormone produces clinical hypothyroidism; excess causes hyperthyroidism.
See also: hormone

thyroid hormone (thīˑ·roid hōrˑ·mōn),

n a combination of two hormones, triiodothyronine (T3) and thyroxine (T4), produced by the thyroid gland. These hormones are responsible for modulating basal metabolic rate and can influence blood pressure, heart rate, temperature, and weight. See also therapy, Gerson.

Patient discussion about thyroid hormone

Q. Has anyone tried natural hormones for hypo-thyroidism or fibromyalgia? I am on the low normal range for hypo-thyroidism (do not take meds for) and was diagnosed years ago with fibromyalgia. I take Ultram for the pain which also helps my fatigue factor but I still feel so sluggish sometimes and just want to sleep. I'm on an anti-depressant as it is. I've been hearing more about natural hormone therapy for these conditions and was wondering if anyone out there has tried this.

A. i have cfids and fibro as well as had my thyroid removed (parathyroid still in place). There really is no substitute for Synthroid that is as effective. There is with cfids and fibro. sensitivity to medications so the dosage normally given would not be the same usually lower dosages or 1/4 to 1/2 tabs. i have started on D-ribose, enada, COQ10, PB 8, Fish Oil with Omegas and primrose oil and B12 compounded shots in addition to other medications to treat medical issues that come along with the diseases. The first are homeopathic and are metabolized at a greater rate than synthetic meds which are often not processed correctly and may build up in your system. It is good to find a specialist [true specialist] or immunologist to help you with the medications and symptomologies that occur. Each person's system is different yet the way that it recognizes medications, food and such is similar and unique to the illnesses.

More discussions about thyroid hormone
References in periodicals archive ?
The team found that higher perchlorate levels were associated with lower levels of thyroid hormones.
While thyroid hormones produced by or given to the mother cross the placenta in only limited amounts, both thyroid antibodies and antithyroid drugs (ATDs) readily cross the placenta and affect fetal thyroid function.
TSH serves as an indicator of thyroid function; it is suppressed (low) when thyroid hormone levels are elevated, and it is elevated when thyroid hormone levels drop," explains Dr.
Furthermore, it is known that cord blood thyroid hormone levels are influenced by different external factors.
Pathophysiological aspects of thyroid hormone disorders/thyroid peroxidase autoantibodies and reproduction.
Thyroid hormone levels improve the prediction of mortality among patients admitted to the intensive care unit.
For example, in Hashimoto's thyroiditis, the most commonly diagnosed type of hypothyroidism, the immune system attacks thyroid cells, inhibiting production of thyroid hormone.
Some foods contain goitrogens, substances that can interfere with thyroid hormone production and may contribute to development of a goiter, or swelling of the thyroid gland, says Susan Allen, RD, of Palm Harbor, Florida.
However, various factors like breed, age, sex and physiological condition affect blood thyroid hormone concentrations by modulating the hypothalamus-pituitary-thyroid axis in small ruminants (Todini 2007).
Results: Both the ethyl acetate fraction and tectoridin activated thyroid- responsive reporters and increased thyroid hormone-dependent proliferation of rat pituitary GH3 cells, indicating modulation of thyroid hormone receptors.
CHILDREN with both a common gene variant and lower thyroid hormone levels are four times more likely to have a low IQ, according to research released this week by Cardiff University.

Full browser ?