Endocrinology Structure Summary

• A summary of structures for endocrinology

Structures

• acr/o means extremities
• -tropin means to stimulate
• gonad/o means ovaries and testicles
• -dipsia means thirst
• crin/o means to secrete
• somat/o means body
• Trop means change
• oxy= swift
• -tocin = labor

Functions and structures

• Overview of the functions and structures of the endocrine system.

Pituitary Gland Function

• The primary function is to secrete hormones controlling the activity of other endocrine glands.

Anterior Lobe

• The adrenocorticotropic hormone stimulates the growth and secretions of the adrenal cortex
• The growth hormone, aka somatotropic hormone, regulates the growth of bone, muscle, and other body tissues.
• The luteinizing hormone stimulates ovulation in females
• In males, luteinizing hormone stimulates the secretion of testosterone.

Posterior Lobe

• The antidiuretic hormone (ADH) is secreted by the hypothalamus and stored in the pituitary gland
• ADH helps control blood pressure by reducing the amount of water excreted through the kidneys
• A diuretic is administered to increase urine secretion.
• Oxytocin stimulates uterine contractions during childbirth
• Oxytocin controls postnatal hemorrhage and stimulates the flow of milk from the mammary glands
• Pitocin is a synthetic form of oxytocin used to induce or speed up labor.

Pineal Gland Functions and Secretions

• Secretions of this gland influence the sleep-wake cycle.
• Melatonin influences the sleep-wake portions of the circadian cycle
• Circadian cycle refers to biological functions within a 24-hour period.

Thyroid Gland Functions and Secretions

• A primary function is to regulate the body's metabolism.
• The two primary thyroid hormones regulate the rate of metabolism and affect the growth and rate of function of many other body systems

Hormones

• Thyroxine (T4)
• Triiodothyronine (T3)
• Calcitonin, produced by the thyroid gland, works with parathyroid hormone to decrease calcium levels in the blood and tissues
• Calcitonin moves calcium into storage in the bones and teeth

Parathyroid Gland Functions and Secretions

• The primary function of the parathyroid glands is to regulate calcium levels throughout the body.
• These calcium levels are important to the smooth functioning of the muscular and nervous systems.

PTH

• The parathyroid hormone (PTH) works with the hormone calcitonin that is secreted by the thyroid glands.
• Together, they regulate the calcium levels in the blood and tissues.

Thymus Functions and Secretions

• The thymus functions as part of the endocrine system and the immune system.
• It helps develop the body's immune system before birth and in childhood.
• Its function is greatly reduced after puberty, and it slowly turns into fatty tissue
• Thymosin plays an important part in the immune system by stimulating the maturation of lymphocytes into T cells.

Pancreas

• The pancreatic islets are those parts of the pancreas that have endocrine functions
• An islet is a small isolated mass or island of one type of tissue within a larger mass of a different type.

Pancreatic Islets Functions and Secretions

• These islets control the blood glucose levels and glucose metabolism throughout the body
• Glucose
• Glucagon is secreted by alpha cells in response to low glucose levels, increasing glucose by stimulating the liver to convert glycogen into glucose for release.
• Insulin is secreted by beta cells in response to high glucose levels
• When energy is needed, insulin allows glucose to enter the cells to be used as energy
• When additional glucose is not needed, insulin stimulates the liver to convert glucose into glycogen for storage.

Adrenal Glands function

• A primary function is to control electrolyte levels within the body.

Adrenal Cortex Secretions

• Corticosteroids are the steroid hormones produced by the adrenal cortex

Hormones of Adrenal Cortex

• Aldosterone
• Cortisol or hydrocortisone is a corticosteroid that has an anti-inflammatory action.
• It also helps regulate the metabolism of carbohydrates, fats, and proteins in the body.

Adrenal Medulla Secretions

• Epinephrine, also known as adrenaline, stimulates the sympathetic nervous system in response to physical injury or mental stress like fear.
• It makes the heart beat faster, can raise blood pressure, helps the liver release glucose, and limits the release of insulin
• Norepinephrine is both a hormone and a neurohormone
• It is released as a hormone by the adrenal medulla and as a neurohormone by the sympathetic nervous system
• It plays an important role in the “fight-or-flight" response by raising blood pressure, strengthening the heartbeat, and stimulating muscle contractions.

Gonads Secretions

• Progesterone is released during the second half of the menstrual cycle by the corpus luteum in the ovary.
• Its function is to complete the preparation of the uterus for possible pregnancy.

Neurohormones

• Neurohormones are produced and released by neurons in the brain rather than by the endocrine glands, and delivered to organs and tissues through the bloodstream.
• An example is neurohormones secreted by the hypothalamus that control the secretions of the pituitary gland.

Steroid Hormones

• Anabolic Steroids increase strength and muscle mass.
• They are manufactured substances chemically related to male sex hormones, used to treat hormone problems in men and to help the body replace muscle mass lost due to disease.
• Leptin is a hormone secreted by fat cells that is involved in the regulation of appetite.

Pathology of the Pituitary Gland

• Acromegaly is a rare hormonal disorder characterized by abnormal enlargement of the extremities caused by the excessive secretion of growth hormone after puberty.
• Hyperpituitarism is the excess secretion of growth hormone that causes both acromegaly and gigantism, usually caused by a pituitary adenoma.
• A pituitary adenoma is a slow-growing benign tumor of the pituitary gland
• Functional pituitary tumors often produce hormones in large and unregulated amounts and might include ACTH, growth hormones, prolactin, or TSH.
• A prolactinoma is a benign functional pituitary tumor that causes the pituitary gland to produce too much of the lactogenic hormone known as prolactin, which can cause infertility in women, erectile dysfunction in men, and can also impair vision.

Antidiuretic Hormone Conditions

• Diabetes insipidus is an uncommon disorder caused by an insufficient production of the antidiuretic hormone (ADH) or by the inability of the kidneys to respond appropriately to this hormone which causes an imbalance of fluids in the body, leading to extreme thirst and frequent urination.
• Hypothyroidism, aka underactive thyroid, is caused by a deficiency of thyroid secretion with Symptoms including fatigue, depression, sensitivity to cold, and a decreased metabolic rate.
• Hashimoto's disease is an autoimmune disease in which the body's own antibodies attack and destroy the cells of the thyroid gland. This inflammation often leads to hypothyroidism.
• Cretinism is a congenital form of hypothyroidism, and if thyroid hormone replacement is not started soon after birth, cretinism causes arrested physical and mental development.
• Myxedema, which is adult hypothyroidism, is caused by an extreme deficiency of thyroid secretion. Symptoms include swelling, particularly around the eye and cheeks, fatigue, and a subnormal temperature.
• Hyperthyroidism/thyrotoxicosis is the overproduction of thyroid hormones, causing an imbalance of metabolism with symptoms including an increased metabolic rate, sweating, nervousness, and weight loss. The most common cause of hyperthyroidism is Graves' disease
• Exophthalmos is an abnormal protrusion of the eyeball out of the orbit.
• Graves' disease is a disorder of unknown cause in which the immune system attacks the thyroid gland and stimulates it to make excessive amounts of thyroid hormone, resulting in hyperthyroidism and can also cause goiter, exophthalmos or both.
• A thyroid storm/thyrotoxic crisis, is a relatively rare, life-threatening condition caused by exaggerated hyperthyroidism
• Patients may complain of fever, chest pain, palpitations, shortness of breath, tremors, increased sweating, disorientation, and fatigue.
• Hyperparathyroidism, which is the overproduction of the parathyroid hormone, causes the condition known as hypercalcemia, and can result from a disorder of the parathyroid gland or from a disorder elsewhere in the body, such as kidney failure.
• Hypoparathyroidism is caused by an insufficient or absent secretion of the parathyroid hormone and causes hypocalcemia, sometimes leading to tetany, which is the condition of periodic, painful muscle spasms and tremors.
• Thymoma is a tumor on the thymus.
• An insulinoma is a benign tumor of the pancreas that secretes additional insulin, causing hypoglycemia (low blood glucose)
• Hyperglycemia is an abnormally high concentration of glucose in the blood, mainly from Diabetes mellitus and symptoms include polydipsia, polyphagia, and polyuria.
  • Polydipsia is excessive thirst
  • Polyphagia is excessive hunger
  • Polyuria is excessive urination
• Dlabetes mellitus, the most common endocrine system disease, is a group of metabolic disorders characterized by hyperglycemia resulting from defects in the body's production of insulin (type 1) or its ability to use it properly (type 2)
• Type 1 Diabetes is an autoimmune insulin deficiency disorder caused by the destruction of pancreatic islet beta cells.
• Type 2 diabetes is an insulin resistance disorder with insulin being produced, but body not able to effectively use it.
• Addison's disease occurs when the adrenal glands do not produce enough of the hormones cortisol or aldosterone.
• This potentially life-threatening condition is characterized by chronic, worsening fatigue and muscle weakness; loss of appetite; low blood pressure and weight loss.
• Many patients also develop patches of dark skin.
• Cushing's syndrome/hypercortisolism is caused by prolonged exposure to high levels of cortisol.
• Cortisol has an anti-inflammatory action and helps regulate the metabolism of carbohydrates, fats, and proteins in the body Signs include a rounded red face.
• Aldosteronism is the abnormality of the electrolyte balance that is caused by the excessive secretion of aldosterone

Blood tests

• Fructosamine test measures average glucose levels over the previous three weeks.