In this text you will find a summary of the endocrine system : what it is and what its functions are in the human body. Also see their structure and how each one works. See below!
The endocrine system is complex, with a large number of endocrine glands. The hormones produced by these glands influence practically all of the body’s physiological functions, also interacting with the nervous system.
The nervous system can provide the endocrine system with information about the external environment and the endocrine system can regulate the body’s response to this information. In addition to acting on non-endocrine organs, some hormones act on other endocrine glands, controlling the secretion of other hormones.
The endocrine system is a system that acts in the synthesis of hormones, through glands, which are released into the bloodstream. Through the bloodstream, hormonal secretions will be directed to specific organs, where they will act according to their specific function. A deficit or excess of hormones can cause diseases and physiological changes in humans.
See also: Discover all the vital organs of the human body
Endocrine system
Hormones that are produced by the glands of the endocrine system can stimulate the secretion of other endocrine glands. When this occurs, these hormones are called tropic hormones and are produced by the adenohypophysis. Tropic hormones are:
1- Thyroidotropic : acts on the thyroid gland;
2- Adrenocorticotropic : acts on the cortex of the adrenal glands;
3- Gonadotropic : acts on the male (testicles) and female (ovaries) gonads.
There are organs that synthesize hormones, acting secondarily as endocrine organs. This is the case with the heart, stomach, small intestine and kidneys. The hypothalamus, a region of the brain, also produces hormones.
Endocrine structures
There are structures, such as glands and organs, that produce the hormones of the endocrine system. Below is a summary of the main hormone-producing structures, where and how they act.
1- Pituitary gland (pituitary gland) : located at the base of the skull, it is approximately the size of a pea and connects to the hypothalamus by a stalk. It has two well-developed lobes: the anterior, adenohypophysis, and the posterior, neurohypophysis. Only the adenohypophysis produces hormones. Hormones produced: adrenocorticotropic (ACTH), thyroidotropic (TSH), follicle stimulating (FSH), luteinizing (LH), growth hormone (GSH) and prolactin. Functions: ACTH = acts on the adrenals to control the body’s water balance; TSH = acts on the thyroid gland, increasing the rate of metabolism; FSH = in men, contributes to spermatogenesis in the presence of testosterone. In women, it stimulates ovarian follicles; LH = acts on the gonads, stimulating their development. Stimulates the production of androgens (male sex hormones), mainly testosterone; GSH = stimulates growth. Its excess during puberty causes gigantism and its lack causes dwarfism. In adults, excess of this hormone can cause abnormal growth in some regions of the body, such as the jaw, hands and feet, an anomaly called acromegaly; Prolactin = stimulates milk secretion in mammals.
2- Hypothalamus : region of the brain where hormones are produced that are stored in the neurohypophysis or act on the adenohypophysis, stimulating or inhibiting its secretions. These are generically called releasing hormones. Hormones produced: oxytocin and antidiuretic hormone (ADH) or vasopressin. Functions: oxytocin = stored in the neurohypophysis, stimulates uterine contractions; ADH = stored in the neurohypophysis, stimulates the reabsorption of water through the kidney collecting ducts, making urine more concentrated. A lack of this hormone causes the disease diabetes insipidus, in which the person experiences a large increase in urinary flow, causing a lot of thirst, generally accompanied by a large appetite and loss of muscle strength.
3- Thyroid gland: located in the anterior portion of the neck, its functioning is stimulated by the thyroidotropic hormone produced by the pituitary gland. Hormones produced: thyroxine (T4), triiodothyronine (T3) and calcitonin. Hormones produced: T4 and T3 = act on metabolism. When in excess, they cause hyperthyroidism (excessive nervousness, increased heart rate and weight loss). When insufficient, they cause hypothyroidism (dry skin, excessive tiredness and intolerance to cold) and goiter, which has been avoided by adding iodine to table salt. In childhood, it can cause cretinism, characterized by mental deficiency and dwarfism; Calcitonin = decreases the calcium content in the blood when this ion is in excess.
See also: Hormones
4- Parathyroid glands : two pairs of small structures located on the posterior surface of the thyroid gland. Hormone produced: parathormone (parathyroid hormone). Functions: increases the calcium content in the blood, when this ion is in low concentration. Its mechanism of action is antagonistic to that of calcitonin.
5- Adrenal glands : two, one over each of the kidneys. Formed by two distinct regions: the cortical (peripheral) and the medullary (central). Hormones produced: Glucocorticoids, mineralocorticoids (the main one is aldosterone) – in the cortex and male sex hormones (androgens), adrenaline (epinephrine) – in the medulla. Functions: glucocorticoids = related to glucose metabolism, they also act as anti-inflammatory drugs; mineralocorticoids = act to control the levels of sodium and potassium ions in the blood, interfering with the retention or loss of water by the body; androgens = act on male secondary sexual characteristics. Excess of these hormones in women can cause the appearance of a beard and other secondary masculine characteristics; epinephrine = determines peripheral vasoconstriction, tachycardia, rapid increase in metabolic rate, increased alertness and decreased digestive and renal activities.
6- Pancreas : mixed gland. The endocrine region comprises the pancreatic islands (islets of Langerhans). Hormones produced: insulin and glucagon. Functions: Insulin = reduces blood glucose concentration. Its deficiency causes an increase in blood sugar, which is characteristic of type I diabetes mellitus. In type II or adult diabetes mellitus there is no lack of insulin, but its use is compromised; Glucagon = increases blood glucose level.
7- Pineal gland (epiphysis) : small gland located at the base of the brain. Hormone produced: melatonin = interferes with the immune, hormonal and nervous systems and sleep regulation.
8- Thymus : lymphoid organ particularly important for the child’s immune defense. In adults it is vestigial. Hormones produced: thymosin and thymopoietin. Functions: both regulate the maturation of T lymphocytes.
9- Testicles : male gonads. Hormone produced: testosterone. Functions: at puberty, it regulates the appearance of secondary sexual characteristics and stimulates spermatogenesis. Maintains metabolism by promoting protein synthesis in the muscular system, increasing muscle mass.
10- Ovaries : female gonads. The interaction of gonadotropic hormones with those produced by the ovary determines a series of changes in the female genital system, giving rise to the menstrual cycle. Hormones produced: estrogen (female sex hormone), progesterone (female sex hormone) and chorionic gonadotropin (HCG). Functions: estrogen = at puberty, it is responsible for the appearance of secondary sexual characteristics. During the menstrual cycle, it stimulates the growth of the uterus wall (endometrium), which prepares itself for the eventual reception of the embryo; Progesterone = keeps the endometrium developed. The low level of progesterone eliminates the stimulus that kept the endometrium developed, which is on the verge of desquamation (menstruation); HCG = stimulates the production of progesterone, which maintains pregnancy. HCG begins to be formed right at the beginning of the placenta formation.