Biology 30-1: Endocrine System - Hormones

ACTH

Adrenocorticotropic Hormone: From the Anterior Pituitary Gland, Targets the Adrenal Cortex, stimulates adrenal glands to release cortisol which helps your body manage physical and emotional stress, control blood sugar, and regulate metabolism.

Too much: forces metabolism to override, and means your body is trapped in a permanent, exhausting "fight-or-flight" stress state, even when there is nothing to be stressed about.

Too little: means your body doesn't get the signal to produce its essential "survival" hormones, leaving you entirely out of energy.

Glucagon

Glucagon: From the alpha cells of the pancreas, targets the liver and fat tissue, raises blood glucose by stimulating the breakdown of stored glycogen into glucose and the production of new glucose, ensuring the body has enough energy between meals.

Too much: Causes blood sugar to become too high (hyperglycemia) because the liver releases excessive glucose into the bloodstream.

Too little: Makes it harder to raise blood sugar when it drops, increasing the risk of dangerously low blood glucose (hypoglycemia).

Estrogen

Estrogen: Primarily from the ovaries, targets the uterus, breasts, bones, and other tissues, develops female secondary sex characteristics, regulates the menstrual cycle, supports the growth of the uterine lining, and helps maintain bone strength.

Too much: Can cause irregular menstrual cycles, breast tenderness, and excessive growth of the uterine lining.

Too little: Can cause irregular or absent periods, delayed puberty, and reduced bone density, increasing the risk of weak bones.

Testosterone

Testosterone: Primarily from the testes, targets reproductive organs, muscles, bones, and other tissues, develops male secondary sex characteristics such as a deeper voice and facial hair, supports sperm production, and increases muscle and bone growth.

Too much: Can cause acne, increased body hair, and disrupted hormone balance, potentially affecting fertility.

Too little: Can cause delayed puberty, reduced muscle mass and bone density, low energy, and reduced sperm production.

hGH

Human Growth Hormone (hGH): From the anterior pituitary gland, targets bones, muscles, and the liver, stimulates body growth and tissue repair, promotes protein synthesis and muscle development, and signals the liver to produce growth factors that help bones and tissues grow.

Too much: Causes excessive growth; in children, it can lead to gigantism, while in adults, it can cause acromegaly (enlargement of hands, feet, and facial bones).

Too little: In children, causes slowed growth and short stature; in adults, can contribute to reduced muscle mass, increased body fat, and low energy.

Prolactin

Prolactin: From the anterior pituitary gland, targets the mammary glands (breasts), stimulates milk production after childbirth to nourish the baby.

Too much: Can cause unexpected milk production, irregular or absent menstrual periods, and reduced fertility.

Too little: Can prevent or reduce milk production after childbirth.

LH

Luteinizing Hormone (LH): From the anterior pituitary gland, targets the ovaries and testes, triggers ovulation and stimulates progesterone production in females, and stimulates testosterone production in males, supporting reproduction.

Too much: Can cause hormone imbalances and irregular menstrual cycles; persistently elevated LH can be associated with conditions such as PCOS.

Too little: Can prevent ovulation and reduce sex hormone production, potentially causing delayed puberty and reduced fertility.

Ocytocin

Oxytocin: Produced in the hypothalamus and released by the posterior pituitary gland, targets the uterus and mammary glands, stimulates uterine contractions during childbirth and milk release during breastfeeding, and supports social bonding.

Too much: Can cause excessively strong uterine contractions, potentially reducing oxygen supply to the baby during childbirth.

Too little: Can weaken uterine contractions during labour and make milk release during breastfeeding more difficult.

ADH

Antidiuretic Hormone (ADH): Produced in the hypothalamus and released by the posterior pituitary gland, targets the kidneys, increases water reabsorption into the bloodstream, helping the body conserve water and maintain blood pressure.

Too much: Causes excessive water retention, diluting blood sodium levels and potentially leading to confusion and headaches.

Too little: Causes excessive water loss through urine, leading to dehydration, increased thirst, and low blood pressure.

Thyroxine

Thyroxine (T4): From the thyroid gland, targets most body cells, increases metabolic rate and energy use, regulates body temperature, and supports normal growth and brain development.

Too much: Speeds up metabolism excessively, causing weight loss, rapid heartbeat, sweating, and anxiety.

Too little: Slows down metabolism, causing fatigue, weight gain, feeling cold, and slowed growth and development in children.

TSH

Thyroid-Stimulating Hormone (TSH): From the anterior pituitary gland, targets the thyroid gland, stimulates it to produce and release T3 and T4, which regulate metabolism, energy use, and body temperature.

Too much: Overstimulates the thyroid, potentially causing excessive thyroid hormone production, a faster metabolism, and a rapid heartbeat if the thyroid responds normally.

Too little: Reduces stimulation of the thyroid, potentially causing low thyroid hormone levels, a slower metabolism, fatigue, and feeling cold.

Glucocorticoids

Glucocorticoids (e.g., Cortisol): From the adrenal cortex, targets most body tissues, helps the body manage long-term stress, raises blood glucose to provide energy, reduces inflammation, and regulates metabolism.

Too much: Keeps the body in a prolonged stress state, causing high blood sugar, weakened immunity, muscle weakness, and weight gain.

Too little: Reduces the body's ability to maintain blood sugar and blood pressure during stress, causing fatigue, weakness, low blood pressure, and potentially dangerous drops in blood glucose.

Calcitonin

Calcitonin: From the thyroid gland, targets bones and kidneys, lowers blood calcium levels by inhibiting bone breakdown and increasing calcium excretion through the kidneys, helping regulate calcium balance.

Too much: Usually causes few noticeable effects, but may lower blood calcium slightly.

Too little: Usually causes no significant symptoms because parathyroid hormone is more important for regulating blood calcium levels.

PTH

Parathyroid Hormone (PTH): From the parathyroid glands, targets bones, kidneys, and indirectly the intestines, raises blood calcium levels (opposite of calcitonin) by releasing calcium from bones, increasing calcium reabsorption in the kidneys, and activating vitamin D to increase calcium absorption from food.

Too much: Causes excessively high blood calcium, potentially weakening bones and causing kidney stones, fatigue, and muscle weakness.

Too little: Causes low blood calcium, leading to muscle cramps, tingling, and potentially dangerous muscle spasms.

Epinephrine

Epinephrine (Adrenaline): From the adrenal medulla, targets the heart, lungs, liver, and muscles, triggers the “fight-or-flight” response by increasing heart rate, breathing rate, and blood glucose, preparing the body to respond quickly to danger or stress.

Too much: Causes a racing heartbeat, high blood pressure, sweating, and anxiety, keeping the body overly alert.

Too little: Usually has minimal effects because other hormones compensate, but may reduce the body's ability to respond to severe physical stress.

Norepinephrine

Norepinephrine (Noradrenaline): From the adrenal medulla and sympathetic nerve endings, targets the heart and blood vessels, triggers the fight-or-flight response by constricting blood vessels, increasing blood pressure, and promoting alertness during stress.

Too much: Causes high blood pressure, rapid heartbeat, anxiety, and excessive alertness.

Too little: Can contribute to low blood pressure, reduced alertness, and difficulty maintaining focus and mood.

Insulin

Insulin: From the beta cells of the pancreas, targets most body cells, especially muscle, fat, and liver cells, lowers blood glucose by helping cells absorb glucose and encouraging the liver and muscles to store excess glucose as glycogen, maintaining blood sugar homeostasis.

Too much: Can cause dangerously low blood glucose (hypoglycemia), leading to shakiness, dizziness, confusion, and potentially unconsciousness.

Too little: Causes high blood glucose (hyperglycemia) because glucose cannot be regulated properly, potentially leading to diabetes, excessive thirst, frequent urination, and fatigue.

FSH

Follicle-Stimulating Hormone (FSH): From the anterior pituitary gland, targets the ovaries and testes, stimulates egg follicle development and estrogen production in females, and supports sperm production in males, helping regulate reproduction and fertility.

Too much: Can indicate reduced function of the ovaries or testes, often due to the body trying to stimulate them harder.

Too little: Can delay puberty, disrupt egg development and menstrual cycles, and reduce sperm production and fertility.

Mineralocorticoids

Mineralocorticoids (e.g., Aldosterone): From the adrenal cortex, targets the kidneys, increases sodium reabsorption and potassium excretion, causing water to follow sodium back into the bloodstream, maintaining blood volume, blood pressure, and electrolyte balance.

Too much: Causes excessive sodium and water retention, leading to high blood pressure and low potassium levels, which can cause muscle weakness.

Too little: Causes excessive sodium and water loss, leading to dehydration, low blood pressure, high potassium levels, and muscle weakness.

Tropic vs. Non tropic Hormones

Tropic hormones: Hormones that target other endocrine glands and stimulate them to release their own hormones.

Examples: TSH, ACTH, FSH, and LH.

Non-tropic hormones: Hormones that act directly on target tissues rather than stimulating another endocrine gland to release hormones.

Examples of non-tropic hormones:

• Growth hormone (hGH): Stimulates growth of bones and muscles.

• Prolactin: Stimulates milk production in the mammary glands.

• Oxytocin: Stimulates uterine contractions and milk release.

• ADH: Increases water reabsorption in the kidneys.