Endocrine System General Questions

What is the main purpose of the Endocrine system?

• Main function: Production and regulation of hormones.

• Hormones: Chemical messengers that regulate body functions.

• 6 functions of hormones:

  1. Growth

  2. Development

  3. Mood

  4. Tissue function

  5. Metabolism

  6. Sexual function (males and females)

Memory trick: G-D-M-T-M-S

Remember: The endocrine system produces and regulates hormones that control various body functions.

What are the main problems that can occur with the endocrine system?

• Hypersecretion: Excessive hormone secretion.

• Hyposecretion: Insufficient hormone secretion.

• Treatment: Controlling hormone secretion can help treat endocrine disorders.

Memory trick: Hyper = Too much; Hypo = Too little.

What works with both the endocrine and exocrine systems? How?

• Purpose: Maintain homeostasis (stable internal body conditions).

• Cooperation: The nervous, endocrine, and exocrine systems work together.

• Feedback loops: Help regulate body functions through:

  • Negative feedback: Reverses a change to maintain balance.

  • Positive feedback: Amplifies a change until a specific outcome is reached.

Memory trick: Negative = Reverse; Positive = Amplify

How does a negative feedback work? Example?

• Meaning: Reverses a change to restore or maintain homeostasis.

• Process: Nervous system detects a harmful change → activates a response → reverses the change.

• Example: Hot day → body temperature rises → nervous system activates sweat glands → sweating cools the body → temperature decreases.

Remember: Negative = Reverses the change.

How does a positive feedback look work? Example?

Positive Feedback Loop

• Meaning: Strengthens or accelerates a change until a specific outcome is reached.

• Process: Stimulus → response → stronger stimulus → continued response.

• Example (Childbirth): Oxytocin released → uterine contractions → cervix stretches → more oxytocin released → stronger contractions → baby is born.

Remember: Positive = Amplifies the change

What is the Hypothalamus?

• Location: Center of the brain, below the thalamus; almond-sized.

• Main role: Connects the nervous and endocrine systems.

• Releasing hormones: Start hormone production and release (ON).

• Inhibiting hormones: Stop hormone production and release (OFF).

Remember: Hypothalamus = Hormone ON/OFF switch

What is the hormone Corticotropin-Releasing Hormone (CRH)?

Stimulates the adrenal glands to release corticosteroids

What is Gonadotropin-Releasing Hormone (GnRH)?

Stimulates the anterior pituitary to release hormones that are essential in proper function of the ovaries and testes.

What are Growth Hormone–Releasing Hormone (GH-RH) and Growth Hormone–Inhibiting Hormone (GH-IH)?

These hormones either prompt or inhibit the release of growth hormones from the anterior pituitary

What is Prolactin-Releasing Hormone (PRH) and Prolactin-Inhibiting Hormone (PIH)?

PRH stimulates breast milk production, whereas PIH stops the production of breast milk.

What is Thyrotropin-Releasing Hormone (TRH)?

Triggers the release of the thyroid-stimulating hormone, which is produced by the anterior pituitary

What are the 2 hormones of the Hypothalamus?

• ADH (Antidiuretic Hormone): Increases water reabsorption by the kidneys.

• Oxytocin: Helps with childbirth, trust, and bonding.

Important: Both hormones are produced by the hypothalamus but stored and released by the pituitary gland.

Memory trick: ADH = Water | Oxytocin = Birth & Bonding

What is the pituitary gland?

• Location: Base of the brain, in the sella turcica of the sphenoid bone.

• Nickname: Master gland — regulates other endocrine glands.

• Connection: Attached to the hypothalamus by the infundibulum (stalk).

• Two lobes:

  • Anterior lobe: Front portion.

  • Posterior lobe: Back portion.

Remember: Pituitary = Master gland; infundibulum = connecting stalk

What is the Anterior Pituitary Gland (Adenohypophysis)?

• Function: Secretes hormones that promote the growth of bones, muscles, and organs.

• Regulates: Growth and development of the thyroid gland, sex glands, and adrenal cortex.

Memory trick: Anterior pituitary = Body growth + Gland development

What is Growth Hormone (GH / Somatotropic Hormone)?

• Function: Promotes bone, muscle, and organ growth in children; maintains bone and muscle mass and breaks down fats (lipolysis) in adults.

• Hyposecretion (too little): Dwarfism.

• Hypersecretion (too much):

  • Children: Gigantism.

  • Adults: Acromegaly.

Memory trick: GH = Growth; Too little → Dwarfism; Too much → Gigantism (children) / Acromegaly (adults).

What is Adrenocorticotropic Hormone (ACTH)?

Function: Stimulates the adrenal cortex to produce hormones and supports the growth and development of its middle and inner layers.

Memory trick: ACTH = Activates the Adrenal Cortex

What is Thyroid-Stimulating Hormone (TSH)?

Function: Promotes the growth and development of the thyroid gland and stimulates thyroid hormone production to regulate metabolism.

Memory trick: TSH = Thyroid + Metabolism

What is Follicle-Stimulating Hormone (FSH)?

• Function: A gonadotropic hormone that stimulates ovarian follicle and egg development in females and sperm production in males.

• Works with: Luteinizing hormone (LH).

Memory trick: FSH = Follicles in females + Sperm in males.

What is Luteinizing Hormone (LH)?

• Females: Helps mature ovarian follicles and stimulates formation of the corpus luteum, which secretes progesterone.

• Males: Stimulates testosterone production.

Memory trick: LH = Luteum in females + Testosterone in males

What is Prolactin (PRL) / Lactogenic Hormone?

Function: Stimulates the mammary glands to produce milk after childbirth.

Memory trick: PRL = Production of milk

What is Melanocyte-Stimulating Hormone (MSH)?

• Function: Regulates skin pigmentation by influencing melanin production in the epidermis.

• Melanin: Helps protect the skin from sunlight (UV radiation).

Memory trick: MSH = Melanin + Skin color

What is the Posterior Pituitary gland (Neurohypophysis)?

Function: Stores and releases ADH and oxytocin, which are produced by the hypothalamus.

Memory trick: Posterior pituitary = Stores & releases 2 hormones

What is the Pineal Gland?

• Location: Posterior end of the corpus callosum in the brain.

• Hormone: Melatonin.

• Functions:

  • Regulates the circadian rhythm (24-hour sleep-wake cycle).

  • Helps regulate reproduction by inhibiting some secretion of LH and FSH.

Memory trick: Pineal = Melatonin + Body clock + Reproductive cycle

What is the Thyroid Gland?

• Meaning: “Shield-shaped” (Greek); butterfly-shaped.

• Size: Largest endocrine gland.

• Location: In front of the trachea, just below the thyroid cartilage.

• Structure: 2 lobes connected by the isthmus.

• Main function: Regulates body metabolism.

• 3 hormones:

  • Thyroxine (T4)

  • Triiodothyronine (T3)

  • Calcitonin — helps lower blood calcium levels.

Memory trick: Thyroid = Metabolism + T3, T4, Calcitonin

What are Thyroid Hormones: T4 & T3?

• Thyroxine (T4) & Triiodothyronine (T3): Regulate the basal metabolic rate (BMR) — how quickly the body uses energy.

• Iodine: Needed to produce these hormones. T4 has 4 iodine atoms; T3 has 3.

• Functions: Increase cellular energy production, protein synthesis, and tissue repair.

Memory trick: T4 = 4 iodine atoms; T3 = 3 iodine atoms. Both regulate metabolism.

What are some disorders caused by the Thyroid hormones?

• Hyposecretion (too little): Cretinism (congenital hypothyroidism), myxedema, and Hashimoto’s thyroiditis.

• Hypersecretion (too much): Hyperthyroidism (thyrotoxicosis), Graves’ disease, exophthalmic goiter, and toxic goiter.

What is Calcitonin?

• Function: Helps regulate calcium levels and bone metabolism by lowering blood calcium.

• Important correction: Cretinism, myxedema, and Hashimoto’s thyroiditis are associated with low thyroid hormone levels (T3 and T4), not calcitonin deficiency.

Memory trick: Calcitonin = Calcium down, bones protected

What are the Parathyroid Glands?

• Location: 4 small glands on the posterior (back) surface of the thyroid.

• Hormone: Parathyroid hormone (PTH / parathormone).

  • Function: Regulates calcium in the blood and bones. Calcium is essential for bone strength, muscle contraction, and nerve impulses

PTH = Pulls calcium into the blood

What are some disorders relating to the parathyroid glands?

• Hyposecretion (too little PTH): Hypoparathyroidism → tetany (muscle twitching/spasms).

• Hypersecretion (too much PTH): Hyperparathyroidism → osteoporosis, kidney stones, and hypercalcemia (high blood calcium)

What is the pancreas?

• Type: Both an endocrine and exocrine gland.

• Exocrine function: Releases digestive juices into the small intestine through ducts.

• Endocrine function: The islets of Langerhans secrete hormones directly into the bloodstream.

Memory trick: Exocrine = Ducts (digestion) | Endocrine = Blood (hormones)

What are the Islets of Langerhans (Pancreas)?

• Alpha cells: Secrete glucagon → raises blood sugar by converting glycogen into glucose.

• Beta cells: Secrete insulin → lowers blood sugar by helping cells absorb glucose.

• Delta cells: Secrete somatostatin → inhibits the release of insulin and glucagon when needed.

• PP and D1 cells: Additional cell types with less-understood functions.

Memory trick:

• Alpha = Adds sugar ⬆

• Beta = Brings sugar down ⬇

• Delta = Dials down hormone release

What happens if the pancreas has hormone imbalances?

• Cause: Too little or too much hormone secretion can disrupt blood glucose levels.

• Insulin hyposecretion: Causes dangerously high blood sugar.

• Treatment: Synthetic insulin may be injected subcutaneously (under the skin) when the body does not produce enough insulin.

• Insulin-dependent diabetes: Requires insulin therapy to help control blood glucose.

Memory trick: Low insulin = High blood sugar ⬆ | Insulin injection = Helps lower blood sugar ⬇

What are the Adrenal Glands?

• Location: On top of each kidney.

• Structure: 2 parts — cortex (outer) and medulla (inner)

What does the Adrenal Cortex — Outer produce?

• Glucocorticoids: Cortisol, corticosterone.

• Mineralocorticoids: Aldosterone.

• Androgens: Sex hormones.

• Function: Regulates metabolism, salt/water balance, and other body functions

Memory trick: Cortex = C-G-M-A (Cortex, Glucocorticoids, Mineralocorticoids, Androgens)

What is the Adrenal Medulla — Inner function?

• Function: Produces, stores, and releases catecholamines during physical or emotional stress.

• High catecholamine levels: May indicate extreme stress, acute anxiety, or rare tumors.

Memory trick: Medulla = Stress response

What is and where is Cortisol made?

Made in the adrenal cortex

• A steroid that is essential in the metabolism of carbohydrates, fats, and protein.

• Increases blood sugar levels by stimulating glucose secretion from the liver; transports amino acids for energy storage.

• Acts as an antiinflammatory agent.

What is and where is Corticosterone made?

Made in the adrenal cortex

• Uses carbohydrates; absorbs glucose.

• Allows the liver to form glucose from substances other than carbohydrates (gluconeogenesis).

What is and where is Aldosterone made?

Made in adrenal cortex

• Regulates electrolyte and water balance.

• Promotes sodium and chloride retention.

• Promotes potassium excretion.

What are and where are Androgens produced?

Made in the adrenal cortex

• Promote the development of primary and secondary male characteristics.

• Main androgens are testosterone and androsterone.

What is and where is Dopamine made?

Made in adrenal medulla.

• Elevates blood pressure through vasoconstriction.

• Increases cardiac and urine output.

• Synthetic dopamine is administered in the treatment of shock.

What is and where is Epinephrine made?

Made in adrenal medulla.

• Also known as adrenaline.

• Responsible for fight-or-flight response.

• Elevates heart rate, blood pressure.

• Dilates bronchial tubes.

• Synthetic epinephrine is administered during emergencies such as cardiac shock and anaphylaxis.

What is and where is Norepinephrine made?

Made in the adrenal medulla.

• Causes vasoconstriction.

• Elevates heart rate, blood pressure, and cardiac output.

• Increases the breakdown of glycogen (glycogenolysis).

What are the ovaries?

• Function: Primary female reproductive organs; produce estrogen and progesterone.

• Estrogen: Secreted by Graafian follicles; promotes female secondary sex characteristics.

• Progesterone: Secreted by the corpus luteum; prepares the uterus for pregnancy.

• Other functions: Supports sexual desire, body hair growth, breast development, feminine body features, and mammary gland development.

Memory trick: Estrogen = Female features | Progesterone = Pregnancy preparation

What are the testes?

• Location: Inside the male scrotum.

• Hormone: Testosterone.

• Functions:

  • Promotes growth and development of male reproductive organs.

  • Supports sexual desire and sexual intercourse.

  • Develops male secondary sex characteristics, including a deeper voice, body hair, and masculine body features.

Memory trick: Testosterone = Male organs + Male characteristics

What is the placenta?

• Function: Connects mother and fetus and enables nutrient and oxygen exchange.

• Present: Only during pregnancy.

• Hormones produced: Estrogen, progesterone, and human chorionic gonadotropin (hCG).

• hCG: Helps maintain early pregnancy and supports the developing fetus.

Memory trick: Placenta = Pregnancy + Hormones + Nutrient exchange

What is the Gastrointestinal (GI) mucosa?

• Location: Endocrine cells in the mucosal lining of the stomach and small intestine.

• Function: Help regulate digestion.

• 4 hormones:

  • Gastrin

  • Secretin

  • Cholecystokinin (CCK)

  • Enterogastrone

Memory trick: G-S-C-E = the 4 GI hormones

What is and where is Gastrin made?

Made in the pyloric area between the stomach and the small intestine.

• Stimulates gastric acid secretion to aid in the breakdown and digestion of food.

What is and where is Secretin made?

Made in the Duodenum and jejunum

• Stimulates the release of water and bicarbonate from the pancreas to aid digestion

What is and where is Cholecystokinin made?

Made in the Duodenum

• Activates the gallbladder to release bile and the pancreas to release digestive enzymes when fatty acids are present in the small intestine.

What is and where is Enterogastrone made?

Made in the Duodenum

• Regulates gastric secretions specifically by inhibiting gastric motility and other gastric hormones

What is the Thymus Gland?

• Location: Mediastinum, in front of and above the heart.

• Functions: Both lymphatic (immune) and endocrine.

• Hormones:

  • Thymosin: Promotes maturation of T lymphocytes.

  • Thymopoietin: Helps lymphocyte precursors develop into T lymphocytes.

Memory trick: Thymus = T-cell development + Immunity

Acromegaly is a hormonal disorder that commonly affects middle-aged adults and results from the overproduction of growth hormone by the

Anterior pituitary gland

Growth hormone promotes the destruction of fats in adults. What is the name of the process?

Lipolysis

What is the small gland located near the base of the brain in the sella turcica?

Pituitary gland

What primary gland of the endocrine system regulates metabolism?

Thyroid

What gland secretes glucocorticoids (cortisol and corticosterone), mineralocorticoids (aldosterone), and androgens?

Adrenal cortex

What is not a primary gland of the endocrine system?

Placenta

All other endocrine glands are regulated by which gland?

Pituitary

What gland is considered to be both an endo and exocrine gland?

Pancreas

Parathyroid glands secrete which hormone?

Parathyroid hormone (PTH)

What releases dopamine?

Adrenal medulla

What gland might be implicated in problems with sleep cycles?

Pineal

Which hormone works in conjunction with Luteinizing hormone (LH)?

Follicle-stimulating hormone (FSH)

Most of the structures and glands of the endocrine system develop when?

First 3 months of pregnancy

In this disease, the cortex of the adrenal gland is damaged by infections, an autoimmune attack, tumors or other factors, decreasing the production of adrenocortical hormones and causing weight loss.

Addison’s disease

Disorder caused by tumor growing on pituitary gland resulting in hypersecretion of the ACTH hormone.

Cushing’s syndrome

Disease causing nervousness, restlessness, heart palpitations, tremors, and sweating, and can cause a condition known as exophthalmos in which eyes protrude.

Hyperthyroidism

What happens if hypothyroidism is left untreated?

Myxedema

Hyposecretion of T3 and T4 from the thyroid gland can result in what condition?

Goiter