Hormone synthesis is the term used to describe the manufacturing process of hormones. Hormones are biochemical messengers released by hormone-producing cells that produce specific effects on target cells.
What is hormone synthesis?
Hormone synthesis is the term used to describe the manufacturing process of hormones. Figure shows insulin release from pancreas. A wide variety of hormones are formed during hormone synthesis. According to their basic chemical structure, two major groups of hormones can be distinguished. On the one hand there are the peptide hormones and on the other hand the steroid hormones. Steroid hormones are very poorly soluble in water and must therefore be bound to carrier proteins for transport in the blood. The mechanism of action is only triggered in the target cell itself. Peptide hormones are highly water-soluble and do not need to be bound to proteins for transport. They bind directly to the cell surface of their target cell through specific receptors and trigger the mechanism of action there. Hormone synthesis is very different in the two groups. In hormone synthesis, autocrine, endocrine and paracrine hormones are produced. Hormones are called autocrine if they show their effect within the same cell. If neighboring cell assemblies are controlled via the hormone produced, it is referred to as a paracrine hormone. If the hormone reaches the target cell via the blood pathway, it is an endocrine hormone.
Function and task
Peptide hormones are composed of amino acids. Amino acids are the smallest building blocks of proteins. The structure of peptide hormones is genetically encoded. Hormone production occurs in the endoplasmic reticulum of the hormone-producing cell. The endoplasmic reticulum is a small channel system within the cell. In many cells, peptide hormones are produced in intermediate stages. These intermediates are also called prehormones or prohormones. They are stored in the cell’s Golgi apparatus or in small vesicles and activated when needed and converted into the final hormone. In this way, larger amounts of the respective hormone can be produced quickly. Peptide hormones include, for example, insulin, somatostatin or glucagon. In the case of insulin and glucagon in particular, it is important that sufficient quantities of the hormone can be released quickly when needed. Otherwise, hyperglycemia or hypoglycemia will occur after food intake or in situations of physical stress. Steroid hormones are usually produced from cholesterol. The thyroid hormones are an exception to this rule. Although these are counted among the steroid hormones, they are synthesized from so-called tyrosines. The cholesterol for the steroid hormones comes primarily from the liver. The hormones are produced in the mitochondria of the hormone-producing cells. Mitochondria are also called “power plants of the cell” because they supply the cells with energy. Steroid hormones are produced primarily in the adrenal cortex. Examples of steroid hormones are mineralocorticoids such as aldosterone or glucocorticoids such as cortisol. The production of steroid hormones in the adrenal cortex is strongly influenced by a transport protein, the Steroidogenic Acute Regulatory Protein (StAR). This protein rapidly provides cholesterol for hormone synthesis during increased demand. Rapid hormone synthesis of glucocorticoids must be ensured, especially during acute stress responses. Glucocorticoids are also known as stress hormones. They ensure that the body’s energy reserves are released. Vitamin D and vitamin A, which are mistakenly assigned to the vitamins, actually also belong to the steroid hormones. Hormone synthesis is controlled by feedback. In negative feedback, hormone synthesis is stopped or decreased as soon as the target cell shows the desired response. In positive feedback, the response of the target cell increases hormone synthesis. This is especially the case with sex hormones. Important control organs of hormone synthesis are the pituitary gland and the hypothalamus.
Diseases and disorders
Disorders of hormone synthesis can occur with any hormone. Symptoms can be very varied, depending on which hormone is affected by the synthesis disorder. Often, hormone synthesis disorders are caused by diseases of the hormone-producing organ. In type 1 diabetes mellitus, the hormone synthesis of insulin is disturbed.This is an autoimmune disease in which the body’s own immune cells destroy the insulin-producing cells of the pancreas. Insulin synthesis is only possible to a limited extent or not at all. As a result, sugar from the blood can no longer be transported into the cells. This leads to hyperglycemia with typical symptoms such as increased thirst, frequent urination and weight loss. If left untreated, there is a risk of ketoacidosis, a dangerous derailment of the metabolism. A disorder in the synthesis of thyroid hormones can result in hypothyroidism. The synthesis disorder can be congenital, caused by iodine deficiency or an autoimmune disease such as Hashimoto’s thyroiditis. If the hormone synthesis of the thyroid gland is stimulated too much, hyperthyroidism occurs. Here, too, an autoimmune disease, Graves’ disease, can be the cause. Typical symptoms of hyperthyroidism include increased sweating, nervousness, diarrhea, and hair loss.
