Anatomy & Physiology: Endocrine Glands and Hormones

Steroid (lipid-soluble) hormones cross the membrane and bind intracellular receptors, changing gene transcription. Peptide (water-soluble) hormones bind cell-surface receptors and act through second messengers such as cAMP.

Blood glucose rises → insulin is released → glucose falls → insulin release drops.

Oxytocin in labor: contractions push the baby against the cervix, triggering more oxytocin and stronger contractions until birth.

Links the nervous and endocrine systems: its releasing and inhibiting hormones control the anterior pituitary, and it makes ADH and oxytocin.

FSH, LH, ACTH, TSH, prolactin, growth hormone

ADH (vasopressin) and oxytocin. Both are made in the hypothalamus and stored and released by the posterior pituitary.

Pituitary

Makes the kidney collecting ducts more permeable to water (inserts aquaporins), so more water is reabsorbed and urine is concentrated.

Anterior pituitary hormone that stimulates growth of bone and muscle, largely through IGF-1 made by the liver.

Anterior pituitary hormone that stimulates milk production.

Made by beta cells of the pancreatic islets; lowers blood glucose by promoting uptake into cells and storage as glycogen.

Made by alpha cells of the pancreatic islets; raises blood glucose by stimulating glycogen breakdown and gluconeogenesis in the liver.

Type 1: autoimmune destruction of beta cells, so little or no insulin. Type 2: insulin resistance with a relative insulin shortage, strongly linked to obesity.

They raise basal metabolic rate and are needed for normal growth and brain development. They require iodine.

Hypothalamus (TRH) → anterior pituitary (TSH) → thyroid (T3, T4). High T3 and T4 inhibit TRH and TSH release (negative feedback).

Graves: autoimmune hyperthyroidism; antibodies stimulate the TSH receptor (bulging eyes, weight loss, heat intolerance). Hashimoto: autoimmune hypothyroidism (fatigue, weight gain, cold intolerance).

Hormone from thyroid parafollicular (C) cells that lowers blood calcium by inhibiting osteoclasts.

Raises blood calcium: stimulates osteoclasts, increases calcium reabsorption in the kidney and activates vitamin D to boost intestinal absorption.

Zona glomerulosa: mineralocorticoids (aldosterone). Zona fasciculata: glucocorticoids (cortisol). Zona reticularis: androgens.

Mineralocorticoid that makes the kidney reabsorb sodium (and water with it) and secrete potassium, raising blood volume and pressure.

Glucocorticoid stress hormone that raises blood glucose (gluconeogenesis) and suppresses inflammation and immune responses.

Adrenal medulla hormone of fight-or-flight: raises heart rate and blood glucose and dilates the airways.

Cushing: too much cortisol (moon face, central obesity, high glucose, thin skin). Addison: adrenal insufficiency, too little cortisol and aldosterone (low blood pressure, darkened skin, low sodium, high potassium).

Low blood pressure → kidneys release renin → angiotensinogen becomes angiotensin I → ACE (mainly in the lungs) makes angiotensin II → vasoconstriction, aldosterone and ADH release → blood pressure rises.

Diabetes insipidus: too little ADH effect, so large volumes of dilute urine and high serum sodium. SIADH: too much ADH, so water retention, concentrated urine and low serum sodium.

Hormone released by the kidneys when oxygen is low; stimulates red blood cell production in bone marrow.

Pineal gland hormone released in darkness that helps regulate the sleep–wake (circadian) rhythm.

FSH stimulates follicle growth. The mid-cycle LH surge triggers ovulation and forms the corpus luteum.

Hormone mainly from the corpus luteum (and later the placenta) that maintains the uterine lining for pregnancy.

Thymus hormone that helps T lymphocytes mature.