Control & communication · Topic 10 of 18

Endocrine System

Hypothalamus, Pituitary, Thyroid & Parathyroids

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Anatomy & Physiology · endocrine glands

Hypothalamus, Pituitary, Thyroid & Parathyroids

The hypothalamus steers the pituitary; the anterior lobe makes six hormones, the posterior releases ADH and oxytocin, and thyroid T3/T4 set metabolism.

01 · Anterior pituitaryAnterior: GH, TSH, ACTH, FSH, LH, prolactin

02 · Posterior pituitaryPosterior: ADH + oxytocin (made in hypothalamus)

03 · ThyroidThyroid T3 + T4 set the metabolic rate

What it is

Endocrine glands are ductless; hormones ride the blood to target cells must know

Hypothalamus (brain) controls the pituitary — the nerve–hormone link must know

Parts & jobs

Anterior pituitary makes 6: GH, TSH, ACTH, FSH, LH, prolactin must know

Posterior pituitary stores + releases ADH and oxytocin (made in hypothalamus) must know

Pituitary = the "master gland," hanging from the hypothalamus by a stalk

Thyroid: butterfly-shaped, front of the neck below the larynx

The rules

Thyroid T3 and T4 set the metabolic rate (energy used at rest) must know

GH (anterior pituitary) → growth of bone and muscle

TSH → thyroid; ACTH → adrenal cortex (cortisol)

FSH and LH → ovaries and testes (gametes, ovulation, sex hormones)

Prolactin (anterior pituitary) → milk production

Oxytocin (posterior pituitary) → uterine contractions + milk let-down

ADH (vasopressin, posterior pituitary) → kidneys keep water

Thyroid hormones need iodine (T4 = 4 iodines, T3 = 3)

Calcitonin (thyroid C cells) lowers blood calcium

PTH (4 parathyroids, back of the thyroid) raises blood calcium

Don't confuse

Hormones act slower and last longer than nerve signals

PTH or calcitonin?

Commonly confused

	PTH	Calcitonin
Made by	Parathyroid glands (usually 4, behind the thyroid)	Thyroid C (parafollicular) cells
Released when	Blood calcium is low	Blood calcium is high
Blood calcium	Raises it	Lowers it
Bone	Osteoclasts free calcium from bone	Slows osteoclasts, so bone keeps its calcium

Mix-ups to avoid

Prolactin makes milk; oxytocin ejects it

More detail

Show 5 more facts

Hypothalamus → pituitary: TRH→TSH, CRH→ACTH, GnRH→FSH/LH, GHRH→GH

PTH raises calcium via bone, kidneys and activated vitamin D

T4 is more plentiful; T3 is more potent

Anterior lobe gets hypothalamic hormones by a portal blood link

Tropic hormones (TSH, ACTH, FSH, LH) control other glands

Pearl

FLAT PiG lists the anterior pituitary hormones: FSH, LH, ACTH, TSH, prolactin, GH.

Sources · OpenStax Anatomy & Physiology 2e §17.1 An Overview of the Endocrine System · OpenStax Anatomy & Physiology 2e §17.3 The Pituitary Gland and Hypothalamus · OpenStax Anatomy & Physiology 2e §17.4 The Thyroid Gland · OpenStax Anatomy & Physiology 2e §17.5 The Parathyroid Glands · Union Test Prep — HESI A&P study guide p. 2 (endocrine glands and hormones) · Built from the verified NurseSavvy HESI A2 fact map (facts reviewed 2026-10-16). HESI is a trademark of Elsevier; NurseSavvy is not affiliated with Elsevier.

Adrenals, Pancreas, Gonads & Other Glands

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Anatomy & Physiology · endocrine glands

Adrenals, Pancreas, Gonads & Other Glands

The adrenal medulla makes epinephrine; the adrenal cortex makes cortisol and aldosterone; pancreatic islets make insulin (lowers glucose) and glucagon (raises it).

01 · InsulinInsulin (beta cells) lowers blood glucose

02 · GlucagonGlucagon (alpha cells) raises blood glucose

03 · Adrenal medullaMedulla: epinephrine (fight-or-flight)

Parts & jobs

Adrenals sit atop the kidneys: outer cortex, inner medulla must know

The rules

Adrenal medulla → epinephrine + norepinephrine (fight-or-flight) must know

Adrenal cortex → steroids: cortisol, aldosterone, androgens must know

Insulin (beta cells) lowers blood glucose must know

Glucagon (alpha cells) raises blood glucose must know

Cortisol: long-term stress — raises glucose, calms inflammation

Aldosterone (adrenal cortex) → kidneys keep Na⁺, lose K⁺

Epinephrine: ↑ heart rate, ↑ blood pressure, ↑ blood glucose

Insulin: muscle and fat take up glucose; liver stores glycogen

Glucagon: liver breaks glycogen down into glucose

Testes → testosterone; ovaries → estrogen + progesterone

Pineal gland → melatonin (sleep–wake cycle; rises in the dark)

Thymus → thymosins (help T cells develop)

Kidneys → erythropoietin (EPO) → more red blood cells

Heart atria → ANP, which lowers blood volume and pressure

Don't confuse

Pancreas = exocrine (enzymes via a duct) + endocrine (islets)

Insulin or glucagon?

Commonly confused

	Insulin	Glucagon
Made by	Beta cells of the pancreatic islets	Alpha cells of the pancreatic islets
Released when	Blood glucose rises (after eating)	Blood glucose falls (fasting)
Blood glucose	Lowers it	Raises it
Liver	Stores extra glucose as glycogen	Breaks glycogen back into glucose

Mix-ups to avoid

Glucagon = the hormone; glycogen = stored glucose

More detail

Show 4 more facts

Cortex zones out → in: glomerulosa (salt), fasciculata (sugar), reticularis (sex)

Delta cells → somatostatin (curbs insulin and glucagon)

Blood glucose is held near 70–100 mg/dL

Gastrin (stomach), secretin (small intestine), leptin (fat → fullness)

Pearl

Insulin and glucagon push blood glucose in opposite directions: insulin lowers it, glucagon raises it.

Sources · OpenStax Anatomy & Physiology 2e §17.6 The Adrenal Glands · OpenStax Anatomy & Physiology 2e §17.9 The Endocrine Pancreas · OpenStax Anatomy & Physiology 2e §17.7 The Pineal Gland · OpenStax Anatomy & Physiology 2e §17.8 Gonadal and Placental Hormones · OpenStax Anatomy & Physiology 2e §17.10 Organs with Secondary Endocrine Functions · OpenStax Anatomy & Physiology 2e §17.1 An Overview of the Endocrine System · Union Test Prep — HESI A&P study guide p. 2 (endocrine glands and hormones) · Built from the verified NurseSavvy HESI A2 fact map (facts reviewed 2026-10-16). HESI is a trademark of Elsevier; NurseSavvy is not affiliated with Elsevier.

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