This video fills us in on the endocrine system—the system of glands which produce and secrete different types of hormones directly into the bloodstream to regulate the body’s growth, metabolism, and sexual development & function.
Table 1 summarizes the major hormones, their target and their function.
|Table 1. Major Horomes|
|Endocrine Gland||Hormone Released||Chemical Class||Target Tissue/Organ||Major Function of Hormone|
|Hypothalamus||Hypothalamic releasing and inhibiting hormones||Peptide||Anterior pituitary||Regulate anterior pituitary hormone|
|Posterior Pituitary||Antidiuretic (ADH)||Peptide||Kidneys||Stimulates water reabsorption by kidneys|
|Oxytocin||Peptide||Uterus, mammary glands||Stimulates uterine muscle contractions and release of milk by mammary glands|
|Anterior Pituitary||Thyroid stimulating (TSH)||Glycoprotein||Thyroid||Stimulates thyroid|
|Adrenocorticotropic (ACTH)||Peptide||Adrenal cortex||Stimulates adrenal cortex|
|Gonadotropic (FSH, LH)||Glycoprotein||Gonads||Egg and sperm production, sex hormone production|
|Prolactin (PRL)||Protein||Mammary glands||Milk production|
|Growth (GH)||Protein||Soft tissue, bones||Cell division, protein synthesis and bone growth|
|Thyroid||Thyroxine (T4) and Triiodothyronie (T3)||Iodinated amino acid||All tissue||Increase metabolic rate, regulates growth and development|
|Calcitonin||Peptide||Bones, kidneys and intestine||Lowers blood calcium level|
|Parathyroids||Parathyroid (PTH)||Peptide||Bones, kidneys and intestine||Raises blood calcium level|
|Adrenal Cortex||Glucocorticoids (cortisol)||Steroid||All tissue||Raise blood glucose level, stimulates breakdown of protein|
|Mineralocorticoids (aldosterone)||Steroid||Kidneys||Reabsorb sodium and excrete potassium|
|Sex Hormones||Steroid||Gonads, skin, muscles and bones||Stimulates reproductive organs and brings on sex characteristics|
|Adrenal Medulla||Epinephrine and norepinephrine||Modified amino acid||Cardiac and other muscles||Released in emergency situations, raises blood glucose level, “fight or flight” response|
|Pancreas||Insulin||Protein||Liver, muscles, adipose tissue||Lowers blood glucose levels, promotes formation of glycogen|
|Glucagon||Protein||Liver, muscles, adipose tissue||Raises blood glucose levels|
|Testes||Androgens (testosterone)||Steroid||Gonads, skin, muscles and bone||Stimulates male sex characteristics|
|Ovaries||Estrogen and progesterone||Steroid||Gonads, skin, muscles and bones||Stimulates female sex characteristics|
|Thymus||Thymosins||Peptide||T lymphocytes||Stimulates production and maturation of T lymphocytes|
|Pineal Gland||Melatonin||Modified amino acid||Brain||Controls circadian and circannual rhythms, possibly involved in maturation of sexual organs|
Fittingly, the profession that works closely with the endocrine system is known as endocrinology. If you found this body system interesting, you may want to look into this field.
An endocrinologist is a medical doctor who specializes in treating disorders of the endocrine glands, hormone systems, and glucose and lipid metabolic pathways. An endocrine surgeon specializes in the surgical treatment of endocrine diseases and glands. Some of the diseases that are managed by endocrinologists: disorders of the pancreas (diabetes mellitus), disorders of the pituitary (gigantism, acromegaly, and pituitary dwarfism), disorders of the thyroid gland (goiter and Graves’ disease), and disorders of the adrenal glands (Cushing’s disease and Addison’s disease).
Endocrinologists are required to assess patients and diagnose endocrine disorders through extensive use of laboratory tests. Many endocrine diseases are diagnosed using tests that stimulate or suppress endocrine organ functioning. Blood samples are then drawn to determine the effect of stimulating or suppressing an endocrine organ on the production of hormones. For example, to diagnose diabetes mellitus, patients are required to fast for 12 to 24 hours. They are then given a sugary drink, which stimulates the pancreas to produce insulin to decrease blood glucose levels. A blood sample is taken one to two hours after the sugar drink is consumed. If the pancreas is functioning properly, the blood glucose level will be within a normal range. Another example is the A1C test, which can be performed during blood screening. The A1C test measures average blood glucose levels over the past two to three months by examining how well the blood glucose is being managed over a long time.
Once a disease has been diagnosed, endocrinologists can prescribe lifestyle changes and/or medications to treat the disease. Some cases of diabetes mellitus can be managed by exercise, weight loss, and a healthy diet; in other cases, medications may be required to enhance insulin release. If the disease cannot be controlled by these means, the endocrinologist may prescribe insulin injections.
In addition to clinical practice, endocrinologists may also be involved in primary research and development activities. For example, ongoing islet transplant research is investigating how healthy pancreas islet cells may be transplanted into diabetic patients. Successful islet transplants may allow patients to stop taking insulin injections.