More than 50 distinct hormones have been identified in the human body, produced by glands and tissues from your brain down to your kidneys. They fall into three chemical categories, get released by roughly a dozen different organs, and collectively control everything from your heart rate to your appetite to how well you sleep. Here’s a full tour of what your body makes and why.
Three Types of Hormone Molecules
Every hormone in your body belongs to one of three chemical families, and the category determines how it travels through your bloodstream and how quickly it acts.
Peptide hormones are chains of amino acids that dissolve easily in blood. Insulin and glucagon are classic examples. Because they’re water-soluble, they work fast, binding to receptors on the outside of cells and triggering rapid changes.
Steroid hormones are built from cholesterol. Estrogen, testosterone, progesterone, cortisol, and aldosterone all belong to this group. They don’t dissolve well in blood, so they hitch a ride on carrier proteins. Once they reach a cell, they can slip through the cell membrane and change gene activity directly, which is why their effects tend to be slower but longer-lasting.
Amine hormones are derived from single amino acids. This small group includes adrenaline (epinephrine), noradrenaline, dopamine, melatonin, and the thyroid hormones T3 and T4. Some dissolve in blood, others don’t, so their speed of action varies.
Hypothalamus and Pituitary: The Control Center
The hypothalamus, a small region at the base of the brain, acts as the link between your nervous system and your hormone system. It doesn’t send most of its hormones out into the body directly. Instead, it releases signaling hormones that tell the pituitary gland what to do. The pituitary, a pea-sized gland just below it, then produces hormones that travel to distant organs.
The major chains work like this:
- Growth hormone releasing hormone (GHRH) from the hypothalamus triggers the pituitary to release growth hormone (GH), which acts on bones and muscles to stimulate growth.
- Gonadotropin-releasing hormone (GnRH) triggers two pituitary hormones: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). In males, LH drives testosterone production and FSH controls sperm production. In females, both hormones regulate the menstrual cycle and trigger ovulation.
- Corticotropin-releasing hormone (CRH) triggers adrenocorticotropic hormone (ACTH), which travels to the adrenal glands and tells them to release cortisol.
- Thyrotropin-releasing hormone (TRH) triggers thyroid-stimulating hormone (TSH), which tells the thyroid to produce T4 and T3.
The pituitary also releases prolactin (stimulates milk production), oxytocin (involved in labor contractions and social bonding), and antidiuretic hormone (ADH), which tells your kidneys to retain water when you’re dehydrated. Oxytocin and ADH are actually made in the hypothalamus but stored and released from the back portion of the pituitary.
Thyroid Hormones: Your Metabolic Thermostat
The thyroid gland in your neck releases two main hormones: thyroxine (T4) and triiodothyronine (T3). Together, they affect every cell in your body by setting the rate at which you burn calories. Too much thyroid hormone speeds up your metabolism, causing weight loss, a racing heart, and anxiety. Too little slows everything down, leading to fatigue, weight gain, and cold sensitivity.
The thyroid also produces calcitonin, a separate hormone that helps lower calcium levels in the blood when they get too high. Calcitonin isn’t grouped with T3 and T4 and has no effect on metabolism.
Parathyroid Hormones and Calcium Balance
Four tiny parathyroid glands sit behind the thyroid and produce parathyroid hormone (PTH). PTH and vitamin D are the two main regulators of calcium and phosphate in your body. When blood calcium drops, PTH pulls calcium from bone stores, tells the kidneys to hold onto calcium instead of excreting it, and activates vitamin D so your gut can absorb more calcium from food. It’s a tightly controlled feedback loop: when calcium rises back to normal, PTH secretion slows down.
Adrenal Glands: Stress, Blood Pressure, and More
You have two adrenal glands, one on top of each kidney. Each gland has two distinct zones that produce very different hormones.
The outer layer (cortex) makes steroid hormones:
- Cortisol, the primary stress hormone, which also regulates metabolism and immune response.
- Aldosterone, which controls blood pressure by telling the kidneys to retain sodium and water.
- DHEA and other androgens, which serve as precursors to sex hormones.
The inner core (medulla) produces amine hormones that act within seconds:
- Adrenaline (epinephrine), the fight-or-flight hormone that spikes your heart rate and blood sugar.
- Noradrenaline (norepinephrine), which narrows blood vessels and raises blood pressure.
- Dopamine, which also functions as a neurotransmitter in the brain.
Pancreatic Hormones: Blood Sugar Control
Scattered through the pancreas are clusters of endocrine cells called the islets of Langerhans. They produce three key hormones:
- Insulin lowers blood sugar by signaling cells to absorb glucose from the bloodstream.
- Glucagon raises blood sugar by telling the liver to release stored glucose.
- Somatostatin acts as a brake on both insulin and glucagon, preventing either from overreacting.
Insulin and glucagon work in constant opposition to keep blood sugar within a narrow range. When this system breaks down, the result is diabetes.
Reproductive Hormones
The ovaries and testes produce the hormones responsible for puberty, fertility, and sexual function.
Testosterone is made primarily in the testes. It drives the physical changes of male puberty (deeper voice, facial hair, muscle and bone growth) and is essential for sperm production. Women also produce small amounts in the ovaries and adrenal glands.
Estrogen is actually a group of three hormones: estradiol, estrone, and estriol. Estradiol is the most active, responsible for maturing and maintaining the female reproductive system, thickening the uterine lining each month, and triggering egg release. Men produce small amounts as well.
Progesterone is secreted by a temporary gland called the corpus luteum that forms in the ovary after ovulation. It prepares the uterine lining to receive a fertilized egg and prevents contractions that would reject it. During pregnancy, the placenta takes over progesterone production and the hormone helps prepare the breasts for milk production.
Two lesser-known reproductive hormones are relaxin, which loosens the uterine wall and later loosens ligaments during pregnancy, and anti-Müllerian hormone (AMH), which is critical during fetal development for forming male reproductive organs and is used in adults as a marker of ovarian reserve.
Gut and Appetite Hormones
Your digestive tract is one of the largest hormone-producing organs in your body. Several hormones from the gut and from fat tissue work together to regulate hunger and energy balance.
Ghrelin is the only known circulating hormone that increases appetite. It’s produced mainly by cells in the stomach and rises before meals, creating the sensation of hunger. After you eat, ghrelin drops.
Working in the opposite direction, several hormones act as fullness signals:
- GLP-1 (glucagon-like peptide-1) is made by cells in the small intestine and colon after a meal. It slows digestion and signals satiety to the brain. It also enhances insulin release, which is why GLP-1-based medications are used for both diabetes and weight management.
- Peptide YY (PYY) is released from the lower gut, with highest concentrations in the colon and rectum, and reduces appetite after eating.
- Oxyntomodulin is released from the small intestine in proportion to calorie intake and suppresses hunger.
- Pancreatic polypeptide (PP) is released from the pancreas after meals and also promotes satiety.
Leptin, produced by fat cells, acts as a long-term energy gauge. The more fat tissue you carry, the more leptin you produce, signaling the brain to reduce appetite. In obesity, the brain can become less responsive to leptin, disrupting this feedback loop.
Kidney Hormones
The kidneys are best known for filtering blood, but they also produce three important hormones.
Erythropoietin (EPO) stimulates red blood cell production in your bone marrow. When kidney cells detect a drop in oxygen levels, they release EPO to boost red blood cell numbers so more oxygen can be carried through the body. Chronic kidney disease often leads to anemia for this reason.
Renin is the starting point of a chain reaction that controls blood pressure. When the kidneys detect low blood pressure or low sodium, they release renin, which sets off a series of chemical conversions that ultimately produce a powerful blood vessel constrictor called angiotensin II. Angiotensin II also triggers aldosterone release from the adrenal glands, causing the kidneys to retain more sodium and water, raising blood volume and pressure.
Calcitriol, the active form of vitamin D, is produced when the kidneys convert the inactive form into its usable state. Calcitriol increases calcium absorption in the gut, working alongside parathyroid hormone to maintain bone health.
Pineal Gland: Your Sleep Clock
The pineal gland, a tiny structure deep in the brain, produces melatonin. This hormone rises when it gets dark and drops when you’re exposed to light, helping set your sleep-wake cycle. Melatonin doesn’t force you to sleep. It signals to your body that nighttime has arrived, making you feel drowsy and lowering your core temperature. Disruptions to melatonin timing, from shift work, jet lag, or late-night screen exposure, are a common cause of sleep difficulties.
Other Hormone-Producing Tissues
Beyond the major glands, several other organs contribute hormones. The heart produces atrial natriuretic peptide (ANP), which lowers blood pressure by telling the kidneys to excrete more sodium and water. The liver produces insulin-like growth factor 1 (IGF-1) in response to growth hormone, carrying out many of GH’s growth-promoting effects. Fat tissue, beyond leptin, produces adiponectin, which improves insulin sensitivity. Even the skin makes a precursor form of vitamin D when exposed to sunlight, which the liver and kidneys then convert into the active hormone calcitriol.
The thymus gland, active mainly during childhood, produces thymosin, which helps immune cells mature. And the placenta, during pregnancy, acts as a temporary endocrine organ, producing human chorionic gonadotropin (hCG, the hormone detected by pregnancy tests), along with its own estrogen and progesterone.