Human Endocrine System

In adults, an undersecretion can also result in myxedema (physical and mental sluggishness).

Thyroxine oversecretion results in a high metabolic rate and Graves’ disease.

Parathyroid glands

The parathyroid

They are tiny masses of glandular tissue that produce parathyroid hormone, also called parathormone.

Parathyroid hormone regulates calcium metabolism in the body by increasing calcium reabsorption in the kidneys and by increasing the uptake of calcium from the digestive system.

Adrenal glands

The adrenal glands are two pyramid-shaped glands lying atop the kidneys.

The adrenal glands consist of an outer portion, the adrenal cortex, and an inner portion, the medulla.

The adrenal cortex secretes a family of steroids called corticosteroids.

The two main types of steroid hormones are

They accelerate mineral reabsorption in the kidneys.

Mineralocorticoid secretion is regulated by ACTH from the pituitary gland.

Glucocorticoids such as cortisol and cortisone control glucose metabolism and protein synthesis in the body.

Glucocorticoids are also anti-inflammatory agents.

The adrenal medulla produces two hormones: epinephrine (adrenaline) and norepinephrine (noradrenaline).

Epinephrine increases heart rate, blood pressure, and the blood supply to skeletal muscles.

Epinephrine functions in stressful situations to promote the fight-or-flight response.

Norepinephrine intensifies the effects of epinephrine.

Both hormones prolong and intensify the effects of the sympathetic nervous system.

Pancreas

The pancreas is located just behind the stomach.

Its endocrine portion consists of cell clusters called the islets of Langerhans.

The pancreas produces two hormones: insulin and glucagon.

Insulin is a protein that promotes the passage of glucose molecules into the body cells and regulates glucose metabolism.

In the absence of insulin, glucose is removed from the blood and excreted in the kidney, a condition called diabetes mellitus.

Diabetes mellitus is characterized by glucose in the urine, heavy urination, excessive thirst, and a generally sluggish body metabolism.

The second pancreatic hormone, glucagon, stimulates the breakdown of glycogen to glucose in the liver.

It also releases fat from the adipose tissue so the fat can be used for the production of carbohydrates.

Other endocrine glands

Among the other endocrine glands are the ovaries and testes.

The ovaries secrete estrogens, which encourage the development of secondary female characteristics.

The testes secrete androgens, which promote secondary male characteristics.

Testosterone is an important androgen.

The pineal gland is a tiny gland in the midbrain.

Its functions are largely unknown, but it seems to regulate mating behaviors and day-night cycles.

The thymus gland is located in the neck tissues.

It secretes thymosins, which influence the development of the T-lymphocytes of the immune system.

Prostaglandins are hormones secreted by various tissue cells.

These hormones produce their effects on smooth muscles, on various glands, and in reproductive physiology.

Erythropoietin is a hormone produced by the kidney cells.

Erythropoietin functions in the production of red blood cells.

Gastrin and secretin are hormones produced by digestive glands to influence digestive processes.