What Are Hormones And What Do They Do?
Hormones are special chemical messengers in the body that are created in the endocrine glands. These messengers control most major bodily functions, from simple basic needs like hunger to complex systems like reproduction, and even the emotions and mood. Understanding the major hormones and what they do will help patients take control of their health.
The GLANDS & ENDOCRINE System
The best way to answer the question “what are hormones?” is to take a look at some of the major hormonal systems in the body. Hormones are created by glands, which are part of the endocrine system. The main hormone-producing glands are:
- Hypothalamus: The hypothalamus is responsible for body temperature, hunger, moods and the release of hormones from other glands; and also controls thirst, sleep and sex drive.
- Parathyroid: This gland controls the amount of calcium in the body.
- Thymus: This gland plays a role in the function of the adaptive immune system and the maturity of the thymus, and produces T-cells.
- Pancreas: This gland produces the insulin that helps control blood sugar levels.
- Thyroid: The thyroid produces hormones associated with calorie burning and heart rate.
- Adrenal: Adrenal glands produce the hormones that control sex drive and cortisol, the stress hormone.
- Pituitary: Considered the “master control gland,” the pituitary gland controls other glands and makes the hormones that trigger growth.
- Pineal: Also called the thalamus, this gland produces serotonin derivatives of melatonin, which affects sleep.
- Ovaries: Only in women, the ovaries secrete estrogen, testosterone and progesterone, the female sex hormones.
- Testes: Only in men, the testes produce the male sex hormone, testosterone, and produce sperm.
Major Types of Hormones
What do hormones do, exactly? The body has many different hormones, but certain types have a bigger role to play in the body’s health and well-being. Understanding these roles is important for those looking to protect and manage their health.
For women, estrogen (or estradiol) is the main sex hormone. It causes puberty, prepares the body and uterus for pregnancy, and regulates the menstrual cycle. During menopause, estrogen level changes cause many of the uncomfortable symptoms women experience.
Progesterone is similar to estrogen but is not considered the main sex hormone. Like estrogen, it assists with the menstrual cycle and plays a role in pregnancy.
Cortisol has been called the “stress hormone” because of the way it assists the body in responding to stress. This is just one of several functions of this important hormone.
Melatonin levels change throughout the day, increasing after dark to trigger the responses that cause sleep.
Testosterone is the main sex hormone in men. It causes puberty, increases bone density, triggers facial hair growth, and causes muscle mass growth and strength.
What are the functions of the different types of hormone?
|Endocrine gland||Hormone||Main tissues acted on by hormone||Main function of hormones|
|Hypothalamus||Thyrotrophin releasing hormone (TRH)||Anterior pituitary||Stimulates release of thyroid stimulating hormone (TSH) from the anterior pituitary|
|Somatostatin||Anterior pituitary||Inhibitory hormone that prevents release of hormones such as growth hormone from the anterior pituitary|
|Gonadotrophin releasing hormone (GnRH)||Anterior pituitary||Stimulates release of follicle stimulating hormone (FSH) and luteinising hormone (LH) from the anterior pituitary|
|Corticotrophin releasing hormone (CRH)||Anterior pituitary||Stimulates adrenocorticotrophic hormone (ACTH) release from the anterior pituitary|
|Growth Hormone Releasing Hormone (GHRH)||Anterior pituitary||Stimulates release of growth hormone (GH) form the anterior pituitary|
|Anterior pituitary||Thyroid stimulating hormone (TSH)||Thyroid gland||Stimulates release of thyroxine and tri-iodothyronine from the thyroid gland|
|Luteinising hormone (LH)||Ovary/Testis||Females: promotes ovulation of the egg and stimulates oestrogen and progesterone production Males: promotes testosterone release from the testis|
|Follicle stimulating hormone (FSH)||Ovary/Testis||Females: promotes development of eggs and follicles in the ovary prior to ovulationMales: promotes production of testosterone from testis|
|Growth Hormone (GH)||Bones, cartilage, muscle, fat, liver, heart||Acts to promote growth of bones and organs|
|Prolactin (PRL)||Breasts, brain||Stimulates milk production in the breasts and plays a role in sexual behaviour|
|Adrenocortico-trophic hormone (ACTH)||Adrenal glands||Stimulates the adrenal glands to produce mainly cortisol|
|Posterior pituitary||Vasopressin (anti-diuretic hormone, ADH)||Kidney, blood vessels, blood components||Acts to maintain blood pressure by causing the kidney to retain fluid and by constricting blood vessels|
|Oxytocin||Uterus, milk ducts of breasts||Causes ejection of milk from the milk ducts and causes constriction of the uterus during labour|
|Thyroid gland||Thyroxine (T4)||Most tissues||Acts to regulate the body’s metabolic rate|
|Tri-iodothyronine (T3)||Most tissues||Acts to regulate the body’s metabolic rate|
|Parathyroid glands||Parathyroid hormone (PTH)||Kidney, Bone cells||Increases blood calcium levels in the blood when they are low|
|Calcitonin||Kidney, Bone cells||Decreases blood calcium levels when they are high|
|Adrenal cortex||Cortisol||Most tissues||Involved in a huge array of physiological functions including blood pressure regulation, immune system functioning and blood glucose regulation|
|Aldosterone||Kidney||Acts to maintain blood pressure by causing salt and water retention|
|Androgens||Most tissues||Steroid hormones that promote development of male characteristics. Physiological function unclear|
|Adrenal medulla||Adrenaline and noradrenaline (the catecholamines)||Most tissues||Involved in many physiological systems including blood pressure regulation, gastrointestinal movement and patency of the airways|
|Pancreas||Insulin||Muscle, fat tissue||Acts to lower blood glucose levels|
|Glucagon||Liver||Acts to raise blood glucose levels|
|Somatostatin||Pancreas||Acts to inhibit glucagon and insulin release|
|Ovary||Oestrogens||Breast, Uterus, Internal and external genitalia||Acts to promote development of female primary and secondary sexual characteristics. Important role in preparing the uterus for implantation of embryo|
|Progesterone||BreastUterus||Affects female sexual characteristics and important in the maintenance of pregnancy|
|Testis||Testosterone||Sexual organs||Promotes the development of male sexual characteristics including sperm development|
|Stomach||Gastrin||Stomach||Promotes acid secretion in the stomach|
|Serotonin (5-HT)||Stomach||Causes constriction of the stomach muscles|
|Duodenum and jejunum||Secretin||Stomach, Liver||Inhibits secretions from the stomach and increases bile production|
|Cholecystokinin (CCK)||Liver, Pancreas||Stimulates release of bile from the gall bladder and causes the pancreas to release digestive enzymes|
|Kidney||Erythropoietin||Bone marrow||Stimulates red blood cell development in the bone marrow|
|Heart||Atrial natiuretic factor (ANF)||Kidney||Lowers blood pressure by promoting salt and water loss|
|Skin||Vitamin D||Small intestine, Kidney,|
|Stimulates the uptake of calcium in the small intestine, retention of calcium and release of calcium from bone stores|
What is anti-Mullerian hormone?
- Anti-mullerian hormone (AMH) is a protein made by the cells that surround each egg
- AMH is produced the most during the small pre-antral stages
- AMH stops producing as follicles grow and nearly no AMH is produced once a follicle hits 8mm in size
- The more eggs a woman has, the higher her AMH level should be
- A simple blood test can determine a woman’s AMH levels
About eight weeks after conception the human fetus has two sets of ducts, one of which can develop into the male reproductive tract and the other into the female reproductive tract. If the fetus is genetically male (XY chromosomes) then the embryonic testes will produce anti-Müllerian hormone. This causes the Müllerian (female) ducts to disappear – hence the term anti-Müllerian hormone, whilst testosterone produced by the testes causes the male (Wollfian) ducts to survive. The Wollfian ducts go on to develop into the different parts of the male reproductive system: the epididymis, the vas deferens, the seminal vesicles and the prostate gland. In a female fetus (XX chromosomes) the Wollfian ducts disappear (because of the lack of testosterone) and the Müllerian ducts develop into the fallopian tubes, uterus (womb), cervix and the upper part of the vagina.
Anti-Müllerian hormone may also have a role in regulating sex steroid production in puberty and in the adult ovaries and testes. In the ovaries, anti-Müllerian hormone appears to be important in the early stages of development of the follicles, which contain and support the eggs prior to fertilisation. The more ovarian follicles a woman has, the more anti-Müllerian hormone her ovaries can produce, and so AMH can be measured in the bloodstream to assess how many follicles a woman has left in her ovaries: her ‘ovarian reserve’.
DIFFERENT BLOOD TESTS FOR HORMONES
Blood or urine tests can determine the levels of various hormones in the body. This includes reproductive hormones, thyroid hormones, adrenal hormones, pituitary hormones, and many others. For more information, see:
- 17-OH progesterone
- 24-hour urinary aldosterone excretion rate
- 25-OH vitamin D
- Adrenocorticotropic hormone (ACTH)
- ACTH stimulation test
- ACTH suppression test
- Catecholamines – blood
- Catecholamines – urine
- Cortisol level
- Cortisol – urine
- Folicle stimulating hormone (FSH)
- Growth hormone
- HCG (qualitative – blood)
- HCG (qualitative – urine)
- HCG (quantitative)
- Luteinizing hormone (LH)
- LH response to GnRH
- PTH-related peptide
- T3RU test
- Secretin stimulation test
- Thyroid stimulating hormone (TSH)
- Anti Mullerian Hormone (AMH)
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