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Thyroid hormones play a particularly crucial role in brain maturation during fetal development and first few years of postnatal life [28] The thyroid hormones also play a role in maintaining normal sexual function, sleep, and thought patterns. Increased levels are associated with increased speed of thought generation but decreased focus. [27]
The thyroid hormones act on nearly every cell in the body. It acts to increase the basal metabolic rate, affect protein synthesis, help regulate long bone growth (synergy with growth hormone) and neural maturation, and increase the body's sensitivity to catecholamines (such as adrenaline) by permissiveness. [12]
Euthyroidism: Normal thyroid function; Hypothyroidism: Reduced thyroid function primary hypothyroidism: Feedback loop interrupted by low thyroid secretory capacity, e.g. after thyroid surgery or in case of autoimmune thyroiditis; secondary hypothyroidism: Feedback loop interrupted on the level of pituitary, e.g. in anterior pituitary failure
At 20 weeks, the fetus is able to implement feedback mechanisms for the production of thyroid hormones. During fetal development, T 4 is the major thyroid hormone being produced while triiodothyronine (T 3) and its inactive derivative, reverse T 3, are not detected until the third trimester.
The thyroid hormones increase the rate of cellular metabolism, and include thyroxine (T4) and triiodothyronine (T3). Secretion is stimulated by the thyroid-stimulating hormone, secreted by the anterior pituitary. When thyroid levels are high, there is negative feedback that decreases the amount of Thyroid-stimulating hormone secreted.
Thyroid follicular cells form a simple cuboidal epithelium and are arranged in spherical thyroid follicles surrounding a fluid filled space known as the colloid. The interior space formed by the follicular cells is known as the follicular lumen .
Parafollicular cells, also called C cells, are neuroendocrine cells in the thyroid. They are called C cells because the primary function of these cells is to secrete calcitonin. [1] They are located adjacent to the thyroid follicles and reside in the connective tissue. These cells are large and have a pale stain compared with the follicular cells.
Endocrinology (from endocrine + -ology) is a branch of biology and medicine dealing with the endocrine system, its diseases, and its specific secretions known as hormones.It is also concerned with the integration of developmental events proliferation, growth, and differentiation, and the psychological or behavioral activities of metabolism, growth and development, tissue function, sleep ...