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Author: Admin | 2025-04-28
Niva Thyroid Description Niva Thyroid (thyroid tablets, USP)* for oral use is a natural preparation derived from porcine thyroid glands and has a strong, characteristic odor. (T3 liothyronine is approximately four times as potent as T4 levothyroxine on a microgram for microgram basis.) They provide 38 mcg levothyroxine (T4) and 9 mcg liothyronine (T3) per grain of thyroid. The inactive ingredients are microcrystalline cellulose, sodium starch glycolate, povidone, and calcium stearate. Niva Thyroid - Clinical Pharmacology The steps in the synthesis of the thyroid hormones are controlled by thyrotropin (Thyroid Stimulating Hormone, TSH) secreted by the anterior pituitary. This hormone’s secretion is in turn controlled by a feedback mechanism effected by the thyroid hormones themselves and by thyrotropin releasing hormone (TRH), a tripeptide of hypothalamic origin. Endogenous thyroid hormone secretion is suppressed when exogenous thyroid hormones are administered to euthyroid individuals in excess of the normal gland’s secretion. The mechanisms by which thyroid hormones exert their physiologic action are not well understood. These hormones enhance oxygen consumption by most tissues of the body, increase the basal metabolic rate, and the metabolism of carbohydrates, lipids, and proteins. Thus, they exert a profound influence on every organ system in the body and are of particular importance in the development of the central nervous system. The normal thyroid gland contains approximately 200 mcg of levothyroxine (T4) per gram of gland, and 15 mcg of liothyronine (T3) per gram. The ratio of these two hormones in the circulation does not represent the ratio in the thyroid gland, since about 80% of peripheral liothyronine (T3) comes from monodeiodination of levothyroxine (T4). Peripheral monodeiodination of levothyroxine (T4) at the 5 position (inner ring) also results in the formation of reverse liothyronine (T3), which is calorigenically inactive. Liothyronine (T3) levels are low in the fetus and newborn,
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