Endocrine System: Glands, Hormones, Hyper & Hypo Functions

Hypothalamus - Location & Main Function

Location: Base of the brain, above the pituitary gland. Function: Controls the endocrine system by producing releasing and inhibiting hormones that regulate the anterior pituitary; controls body temperature, blood pressure, growth, reproduction, and electrolyte/water balance.

Hypothalamus - Hyperfunction

Excessive releasing hormones overstimulate the pituitary gland, leading to overproduction of downstream hormones (e.g., excess GH, cortisol, or thyroid hormone) causing conditions like Cushing's disease or hyperthyroidism.

Hypothalamus - Hypofunction

Insufficient releasing hormones cause underproduction of pituitary hormones, resulting in deficiencies in growth hormone, thyroid hormone, cortisol, and sex hormones.

Pituitary Gland (Master Gland) - Location & Main Function

Location: Base of the brain, housed in the sella turcica of the sphenoid bone, connected to the hypothalamus. Function: Releases hormones that regulate other endocrine glands; divided into anterior lobe (adenohypophysis) and posterior lobe.

Growth Hormone (GH) / Somatotropin - Function

Stimulates growth of bones and muscles; increases size and division rate of body cells.

Growth Hormone (GH) - Hyperfunction

In children: Gigantism (excessive overall body growth). In adults: Acromegaly (enlarged hands, feet, chin, nose, and forehead after growth plates fuse).

Growth Hormone (GH) - Hypofunction

Pituitary dwarfism: Normal body proportions but overall small size (in children).

Prolactin (PRL) - Function

Stimulates lactation (milk production) in females; stimulates lacrimation (desire to cry). Decreased in adolescent males.

Prolactin (PRL) - Hyperfunction

Inappropriate milk production (galactorrhea); disrupted menstrual cycles and infertility in females.

Prolactin (PRL) - Hypofunction

Failure to produce milk after childbirth.

Thyroid-Stimulating Hormone (TSH) - Function

Stimulates the thyroid gland to release thyroid hormone (T3 and T4).

TSH - Hyperfunction

Overstimulates thyroid leading to hyperthyroidism; in iodine deficiency, excess TSH causes goiter (thyroid gland enlargement).

TSH - Hypofunction

Understimulates thyroid leading to hypothyroidism (low metabolism, fatigue, weight gain).

Adrenocorticotropic Hormone (ACTH) - Function

Acts on the adrenal cortex to stimulate release of cortisol; helps the body cope with stress.

ACTH - Hyperfunction

Excess cortisol release causing Cushing's disease: high blood glucose, high blood pressure, moon face, buffalo hump, features of opposite sex.

ACTH - Hypofunction

Addison's disease: decreased cortisol and mineralocorticoids, causing hypotension, hypoglycemia, and hyperpigmentation.

Follicle-Stimulating Hormone (FSH) - Function

Present in males and females; stimulates maturation of sex cells (sperm and eggs).

FSH - Hyperfunction

Early or excessive sexual maturation (precocious puberty); ovarian hyperstimulation.

FSH - Hypofunction

Infertility; failure to mature sex cells; delayed puberty.

Luteinizing Hormone (LH) / ICSH (males) - Function

Induces ovulation in females; stimulates testosterone production in males.

LH/ICSH - Hyperfunction

Early puberty; polycystic ovary syndrome (PCOS) in females.

LH/ICSH - Hypofunction

No ovulation (anovulation) in females; low testosterone in males; infertility.

Melanocyte-Stimulating Hormone (MSH) - Function

Darkens skin pigmentation; increases during pregnancy. Located in the intermediate lobe of the pituitary.

MSH - Hyperfunction

Hyperpigmentation (darkening of the skin, also seen in Addison's disease).

MSH - Hypofunction

Decreased skin pigmentation.

Antidiuretic Hormone (ADH) / Vasopressin - Function

Released from posterior pituitary; signals kidneys to increase water reabsorption/retention; also raises low blood pressure as vasopressin.

ADH - Hyperfunction

Syndrome of inappropriate ADH (SIADH): excess water retention, low blood sodium (hyponatremia), fluid overload.

ADH - Hypofunction

Diabetes insipidus: frequent urination (polyuria) and excessive thirst (polydipsia); normal blood glucose levels.

Oxytocin - Function

Released from posterior pituitary; stimulates uterine contractions during childbirth; synthetic form (Pitocin) used to induce labor.

Oxytocin - Hyperfunction

Premature or excessively strong uterine contractions; risk of uterine rupture.

Oxytocin - Hypofunction

Weak uterine contractions; prolonged or stalled labor.

Pineal Gland - Location & Main Function

Location: Roof of the third ventricle in the brain. Function: Produces melatonin to regulate circadian sleep-wake cycles; secretion is inhibited by light.

Melatonin - Hyperfunction

Excessive sleepiness; disrupted circadian rhythm; seasonal affective disorder (SAD).

Melatonin - Hypofunction

Insomnia; disrupted sleep cycles.

Thyroid Gland - Location & Main Function

Location: Neck, close to the cricoid cartilage (Adam's apple). Function: Regulates body metabolism through thyroid hormones (T3 and T4); also produces calcitonin to lower blood calcium.

Thyroxine (T4) & Triiodothyronine (T3) - Function

Act on most body cells to increase metabolic rate; require iodine for synthesis; controlled by TSH from the pituitary.

Thyroid Hormone (T3/T4) - Hyperfunction

Hyperthyroidism / Graves' disease: elevated metabolism, rapid heart rate, weight loss, nervousness, exophthalmos (bulging eyes), sweating.

Thyroid Hormone (T3/T4) - Hypofunction

Hypothyroidism: overweight, slow movement, low energy, feeling cold. In adults: Hashimoto's or Myxedema. In children: Cretinism (stunted growth and mental development).

Calcitonin - Function

Secreted by thyroid gland; lowers blood calcium levels; slows osteoclasts to allow osteoblasts to build bone (especially active in children).

Calcitonin - Hyperfunction

Excessively low blood calcium (hypocalcemia); abnormal bone density.

Calcitonin - Hypofunction

Elevated blood calcium; increased bone breakdown.

Goiter

Enlargement of the thyroid gland caused by dietary iodine deficiency. Without iodine, thyroid hormone cannot be produced; lack of feedback causes pituitary to oversecrete TSH, causing thyroid hypertrophy.

Parathyroid Glands - Location & Main Function

Location: Four glands the size of grains of rice attached to the posterior surface of the thyroid gland. Function: Maintain calcium-phosphorus balance through parathyroid hormone (PTH).

Parathyroid Hormone (PTH) - Function

Raises blood calcium levels; antagonistic to calcitonin. Stimulated by low blood calcium (humoral mechanism).

PTH - Hyperfunction

Hyperparathyroidism: increased blood calcium (hypercalcemia); bone weakening as calcium is pulled from bones.

PTH - Hypofunction

Hypoparathyroidism: decreased blood calcium (hypocalcemia); tetany (muscle cramps and spasms).

Thymus Gland - Location & Main Function

Location: Under the sternum, on top of the heart. Function: Acts as an incubator for T-cells (white blood cells) to mature; produces thymosins to assist T-cell maturation; most active in children under age 3, then shrinks in adults.

Thymosin - Hyperfunction

Overactive immune response; potential autoimmune issues.

Thymosin - Hypofunction

Impaired T-cell development; weakened immune system; increased susceptibility to infections.

Adrenal Glands - Location & Main Function

Location: On top of each kidney (one per kidney); have an outer cortex and inner medulla. Function: Cortex produces steroid hormones (mineralocorticoids, glucocorticoids, androgens); medulla produces catecholamines (epinephrine, norepinephrine) in response to sympathetic nervous system stimulation.

Epinephrine (Adrenaline) & Norepinephrine - Function

Secreted by adrenal medulla in response to sympathetic (fight-or-flight) stimulation; powerful cardiac stimulants; raise blood glucose and increase metabolism.

Epinephrine/Norepinephrine - Hyperfunction

Hypertension (high blood pressure), rapid heart rate, anxiety, elevated blood glucose (pheochromocytoma).

Epinephrine/Norepinephrine - Hypofunction

Impaired fight-or-flight response; low blood pressure; fatigue.

Aldosterone (Mineralocorticoid) - Function

Secreted by adrenal cortex; promotes sodium and water reabsorption by the kidneys; water follows salt, increasing blood volume and pressure.

Aldosterone - Hyperfunction

Hyperaldosteronism: high blood pressure, low potassium (hypokalemia), fluid retention.

Aldosterone - Hypofunction

Addison's disease component: low sodium, low blood pressure, dehydration.

Cortisol (Glucocorticoid) - Function

Secreted by adrenal cortex in response to ACTH; stimulates fat and protein catabolism for gluconeogenesis (glucose production); suppresses immune response (anti-inflammatory); also called hydrocortisone.

Cortisol - Hyperfunction

Cushing's syndrome: high blood glucose (diabetogenic), high blood pressure, low immune response, osteoporosis, belly fat, moon face, buffalo hump, and opposite-sex features.

Cortisol - Hypofunction

Addison's disease: low blood glucose, low blood pressure, hyperpigmentation; treated with corticosteroid replacement therapy.

Adrenal Androgens - Function

Male sex hormones (androgens) also produced by adrenal cortex; contribute to male secondary sex characteristics; females also produce estrogen via adrenal cortex.

Adrenal Androgens - Hyperfunction

Virilization in females (facial/body hair, voice deepening, decreased breast size); early puberty in children.

Adrenal Androgens - Hypofunction

Decreased sex drive; decreased body hair.

Pancreas - Location & Main Function

Location: Behind the stomach. Function: Has both exocrine (digestive enzymes) and endocrine functions; islets of Langerhans secrete insulin and glucagon to regulate blood sugar.

Insulin - Function

Signals most body cells to take up glucose from the blood; promotes storage of glucose as glycogen in the liver; lowers blood sugar.

Insulin - Hyperfunction

Hypoglycemia (dangerously low blood sugar); insulin shock; confusion, sweating, unconsciousness.

Insulin - Hypofunction

Hyperglycemia (high blood sugar); diabetes mellitus - Type I (autoimmune destruction of islet cells, requires daily insulin) or Type II (insulin resistance from obesity).

Glucagon - Function

Signals the liver to break down glycogen into glucose; raises blood sugar; antagonistic to insulin.

Glucagon - Hyperfunction

Hyperglycemia; elevated blood glucose levels.

Glucagon - Hypofunction

Severe hypoglycemia; inability to raise blood sugar during fasting.

Diabetes Mellitus - Type I vs. Type II

Type I: Autoimmune destruction of pancreatic islets; develops in children; insulin-dependent (requires daily injections). Type II: Cells become less sensitive to insulin; develops in adults; linked to obesity; treated with diet, exercise, oral meds, or insulin.

Diabetic Coma

Life-threatening complication of diabetes; caused by dangerously high blood sugar (hyperglycemia) or dangerously low blood sugar (hypoglycemia); patient is unconscious and unresponsive; fatal if untreated.

Gonads (Ovaries) - Location & Main Function

Location: Female pelvis. Function: Produce estrogen and progesterone to regulate female reproductive functions and secondary sex characteristics.

Estrogen - Function

Develops and maintains female secondary sex characteristics; regulates menstrual cycle.

Estrogen - Hyperfunction

Early puberty; abnormal menstrual cycles; increased risk of certain cancers.

Estrogen - Hypofunction

Delayed puberty; osteoporosis; menopause symptoms; irregular cycles.

Progesterone - Function

Prepares the uterus for pregnancy by enlarging arteries supplying the endometrium and stimulating growth of endometrial glands.

Progesterone - Hyperfunction

May suppress ovulation; side effects similar to early pregnancy symptoms.

Progesterone - Hypofunction

Inability to maintain uterine lining; miscarriage risk; irregular cycles.

Gonads (Testes) - Location & Main Function

Location: Male scrotum; primary male sex organs (NOT the penis). Function: Produce testosterone to maintain male secondary sex characteristics and sperm production.

Testosterone - Function

Promotes sperm formation; maintains male secondary sex characteristics (muscle mass, body hair, voice deepening).

Testosterone - Hyperfunction

Early puberty in boys; aggression; excessive muscle growth; in females causes virilization. Anabolic steroid abuse (synthetic testosterone at 100x doses) causes rage, liver/kidney disease, cancer, baldness, testicular shrinkage, sterility, and high blood pressure.

Testosterone - Hypofunction

Delayed puberty; low sperm count; decreased muscle mass; infertility; low libido.