Thyroid Hormones: Synthesis, Release and Regulation

The whole issue of hormone supplementation is very complicated and there are no simple answers.

Parathyroid hormone: regulation of synthesis and secretion

act as regulators of many functions including the control of sleep-wake states, breathing, and central chemosensitivity.
Oxyntomodulin hormone - Oxyntomodulin is a hormone found in the gut could help reduce appetite and increase physical activity in overweight and obese people.

The primary synthetic organ of Thyroid Hormones is the thyroid gland which produces about twenty times more T4 compared to T3.


Glucagon secretion is regulated principally by the blood glucose concentration and insulin. Increasing concentrations of each inhibit glucagon secretion. The direction of blood flow in the islets of the pancreas carries insulin from the β cells at the center of the islets to the peripheral α cells, where it suppresses glucagon secretion. Some hormones stimulate glucagon secretion, particularly, catecholamines (including epinephrine), cortisol, and some gastrointestional hormones. In addition, some amino acids stimulate glucagon secretion. Thus, the increased concentration of glucagon that would be expected in the fasted state does not decrease after a high-protein, low glucose meal, and the increased glucagon stimulates gluconeogenesis to maintain blood glucose homeostasis. The relative concentrations of insulin and glucagon in the blood after a mixed meal depend on the composition of the meal, because glucose stimulates insulin secretion and some amino acids stimulate glucagon secretion.

To affect the flux of substrates through a metabolic pathway a hormone must be able to change the rate at which that pathway proceeds. It must affect the activity of specific enzymes or transport proteins to either cause the amount of a substrate to increase (if substrate supply is rate-limiting), change the conformation at the active site by phosphorylating the enzyme, change the concentration of an allosteric effector of the enzyme, or change the amount of an enzyme by inducing or repressing its synthesis or by changing its turnover rate or cellular location. The effects mediated by phosphorylation or changes in the kinetic properties of an enzyme occur rapidly, within minutes, but it may take hours for the induction or repression mechanisms that change the amount of an enzyme in a cell.

Mechanism of Hormone Action (With Feedback Regulation)

Glucagon, a 29 amino acid polypeptide hormone, is synthesized in the α cells of the pancreas by cleavage from a larger preproglucagon protein. Like insulin, it is synthesized in RER and converted to proglucagon as it enters the lumen of the RER. Proteolytic cleavage generates the mature 29-amino acid glucagon and larger glucagon-containing fragments, glucagon-like polypeptides 1 and 2 (GLP-1, GLP-2).

Enzyme Action in the Regulation of Plant Hormone …

(Fernando Mesquita Júnior, Cristiane Queixa Tilelli, Maria Emília Soares Martins-Santos, Valéria Ernestânia Chaves, Department of Basic Health Sciences, Federal University of Mato Grosso, Cuiabá, Mato Grosso, Brazil, and others)

The Human Growth Hormone: Synthesis, Regulation and Health Implications, pp.

Regulation of growth hormone messenger RNA synthesis …

The signaling process is reversed when the secretion of glucagon, which has a half-life in the blood of approximately 4 minutes, declines. The Gα subunit becomes inactive as a result of its GTPase activity, and remains inactive in the absence of activation by glucagon. cAMP is hydrolyzed to AMP by cAMP phosphodiesterase, thereby reducing the levls of cAMP and causing the PKA catalytic subunits to rejoin the repressive regulatory subunits. The concentration of cAMP and other second messengers is balanced by the activities of those processes that synthesize them and those processes that destroy them. In the presence of hormone cAMP synthesis exceeds cAMP destruction and cAMP concentration increases. In the absence of hormone cAMP destruction exceeds cAMP synthesis and cAMP concentration decreases.


Although women using hormones have a different hormonal profile than those not using hormones, plasma sex hormone concentrations appear to be associated with breast cancer risk among post menopausal hormone users.
-- Small synthetic molecules called growth hormone secretagogues (GHSs) stimulate the release of growth hormone from the pituitary gland.


The discovery of ghrelin indicates that the release of growth hormone from the pituitary might be regulated not only by hypothalamic growth hormone -releasing hormone, but also by ghrelin derived from the stomach.