11
Thyroglobulin is then secreted into the follicular cavity where it binds with iodide
by the enzyme action to form iodinated thyroglobulin. Then, the endosome containing the iodinated thyroglobulin is fused with the lysosome to thereby enzymatically
release thyroglobulin from the obtained thyroid hormone. The thyroid hormone is
then released from the cells, and the remaining thyroglobulin is deiodinated and
recycled [9–11].
T3 is accountable for many organs and tissues that affect the human body. In
short, this can be a function of increasing protein synthesis as well as metabolic rate.
T4 deficiency significantly decreases the ability of GH in order to stimulate RNA
formation as well as amino acids uptake. In addition, it is important for normal
organ growth, mainly in closely related regions of the central nervous system
[12, 13].
Calcitonin
Parafollicular cells or C cells are accountable for the formation and secretion of
calcitonin (thyrocalcitonin). Calcitonin, in contrast to parathyroid hormone, lowers
blood calcium levels and maintains calcium homeostasis [14]. Calcitonin (or thyrocalcitonin) lowers the calcium blood level and majorly this calcium is deposited in
bones [15].
Control System for Thyroid Hormone Secretion
Two factors are involved in thyroid hormone secretion. First is the automatic regulation of the thyroid, which can be adjusted according to the range of dietary iodide.
Second one is the production of thyroid stimulating hormone from anterior lobe of
pituitary gland. Additional compounds might play a role in its regulation, e.g., prostaglandins, growth factors, and neurotransmitters but their physiological significance remains to be proven. The amount of iodide is examined by its effect on
thyroid hormone levels circulating in blood and the thyroid itself, thereby reducing
response of thyroid cells to thyroid stimulating hormone. Increased amounts of
iodine involve in inhibiting the secretion of hormones that bind to thyroglobulin,
thereby reducing angiogenesis in the glands. Therefore, patients with hyperthyroidism have taken iodine before surgery [6].
Thyroid hormones (T3 and T4) work in a synergistic manner in order to maintain
negative feedback mechanism of their regulation. Elevated levels of T3 as well as
T4 stimulate the hypothalamus and anterior lobe of pituitary gland to shut down the
secretion of TRH and TSH, respectively. On contrary, decreased levels of T3 and T4
cause the TRH and TSH genes to turn on to enhance their yield, consequently the
levels of T3 and T4 are increased [16].
1 Physiology of Endocrine System and Related Metabolic Disorders
Thyroglobulin is then secreted into the follicular cavity where it binds with iodide
by the enzyme action to form iodinated thyroglobulin. Then, the endosome containing the iodinated thyroglobulin is fused with the lysosome to thereby enzymatically
release thyroglobulin from the obtained thyroid hormone. The thyroid hormone is
then released from the cells, and the remaining thyroglobulin is deiodinated and
recycled [9–11].
T3 is accountable for many organs and tissues that affect the human body. In
short, this can be a function of increasing protein synthesis as well as metabolic rate.
T4 deficiency significantly decreases the ability of GH in order to stimulate RNA
formation as well as amino acids uptake. In addition, it is important for normal
organ growth, mainly in closely related regions of the central nervous system
[12, 13].
Calcitonin
Parafollicular cells or C cells are accountable for the formation and secretion of
calcitonin (thyrocalcitonin). Calcitonin, in contrast to parathyroid hormone, lowers
blood calcium levels and maintains calcium homeostasis [14]. Calcitonin (or thyrocalcitonin) lowers the calcium blood level and majorly this calcium is deposited in
bones [15].
Control System for Thyroid Hormone Secretion
Two factors are involved in thyroid hormone secretion. First is the automatic regulation of the thyroid, which can be adjusted according to the range of dietary iodide.
Second one is the production of thyroid stimulating hormone from anterior lobe of
pituitary gland. Additional compounds might play a role in its regulation, e.g., prostaglandins, growth factors, and neurotransmitters but their physiological significance remains to be proven. The amount of iodide is examined by its effect on
thyroid hormone levels circulating in blood and the thyroid itself, thereby reducing
response of thyroid cells to thyroid stimulating hormone. Increased amounts of
iodine involve in inhibiting the secretion of hormones that bind to thyroglobulin,
thereby reducing angiogenesis in the glands. Therefore, patients with hyperthyroidism have taken iodine before surgery [6].
Thyroid hormones (T3 and T4) work in a synergistic manner in order to maintain
negative feedback mechanism of their regulation. Elevated levels of T3 as well as
T4 stimulate the hypothalamus and anterior lobe of pituitary gland to shut down the
secretion of TRH and TSH, respectively. On contrary, decreased levels of T3 and T4
cause the TRH and TSH genes to turn on to enhance their yield, consequently the
levels of T3 and T4 are increased [16].
1 Physiology of Endocrine System and Related Metabolic Disorders