Exam Questions: Endocrine System

What are peptide & protein hormones made of?

Chains of amino acids; they are water-soluble (hydrophilic).

Why are peptide & protein hormones water-soluble?

So they cannot pass through the membrane.

How do peptide & protein hormones act on target cells?

They travel freely in the bloodstream, bind to cell surface receptors, and activate second messenger systems like cAMP or calcium signaling.

What are steroid hormones made from?

Cholesterol; they are lipid-soluble (hydrophobic).

Why are steroid hormones lipid-soluble?

So they easily pass through the cell membrane.

How do steroid hormones act on target cells?

They travel in the bloodstream bound to carrier proteins, enter cells directly, and regulate gene expression by binding to intracellular receptors.

What are amino acid-derived hormones made from?

Single amino acids (mainly tyrosine or tryptophan).

How do amino acid-derived hormones act?

They can act like peptides or steroids, depending on whether they are water- or lipid-soluble.

Where is the pituitary gland located?

At the base of the brain, just below the hypothalamus.

What is the main function of the pituitary gland?

It controls other endocrine glands and regulates essential body functions.

How does the hypothalamus control the pituitary gland?

• Releases hormones that regulate the anterior pituitary

• Sends nerve signals to control the posterior pituitary

What are the two parts of the pituitary gland?

• Anterior Pituitary (Adenohypophysis)

• Posterior Pituitary (Neurohypophysis)

What does the anterior pituitary do?

It produces and secretes its own hormones in response to signals from the hypothalamus.

What hormones are released by the anterior pituitary?

GH, ACTH, TSH, LH, FSH, PRL

What does the posterior pituitary do?

It stores and releases hormones made by the hypothalamus.

What hormones are released by the posterior pituitary?

ADH and Oxytocin.

What does Growth Hormone (GH) do?

Stimulates growth (bones, muscles, liver).

What does Adrenocorticotropic Hormone (ACTH) do?

Stimulates the adrenal glands to release cortisol (adrenal cortex).

What does Thyroid-Stimulating Hormone (TSH) do?

Stimulates the thyroid gland to produce thyroid hormones T3 & T4 (thyroid gland).

What does Prolactin (PRL) do?

Stimulates milk production in the breast (mammary glands).

Does the posterior pituitary produce its own hormones?

No, it stores and releases hormones made by the hypothalamus.

What does Antidiuretic Hormone (ADH) do?

Decreases urine production (kidneys).

What does Oxytocin do?

Makes smooth muscle contract in the reproductive tract (uterus, mammary glands).

What type of control system regulates pituitary hormone levels?

A negative feedback loop that continuously adjusts hormone production to maintain balance.

How does the thyroid hormone feedback loop start?

The hypothalamus releases TRH (Thyrotropin-Releasing Hormone), beginning the cycle.

What does TRH stimulate the anterior pituitary to do?

Release TSH (Thyroid-Stimulating Hormone).

What does TSH stimulate the thyroid gland to do?

Produce and release T3 and T4, which regulate metabolism.

What happens when T3 and T4 levels become high?

The hypothalamus and pituitary decrease TRH and TSH, reducing thyroid hormone output — completing the cycle.

Where is the thyroid gland located?

In the front of the neck; it is butterfly-shaped.

What is the main function of the thyroid gland?

It regulates metabolism, energy levels, and overall body function.

What is the difference between T4 and T3?

• T4 (Thyroxine) is the inactive form.

• T3 (Triiodothyronine) is the active form, converted from T4 in tissues.

Which thyroid hormone is primarily responsible for regulating metabolism?

T3

Where are the four parathyroid glands located?

On the back of the thyroid gland in the neck.

What is the main function of the parathyroid glands?

To regulate calcium homeostasis.

What is the main function of the parathyroid glands?

They monitor blood calcium levels and release PTH when calcium is low.

Where are the adrenal glands located?

On top of each kidney.

What do the adrenal glands do?

They produce hormones that regulate stress response, metabolism, immune function, and blood pressure.

What do adrenal cortex hormones do?

Cortisol and aldosterone help with long-term stress and fluid balance.

What do adrenal medulla hormones do?

Adrenaline and norepinephrine prepare the body for immediate action (short-term stress).

What cells produce insulin?

Beta (β) cells of the pancreas.

What is the main function of insulin?

Lowers blood glucose levels

How does insulin lower blood glucose?

By promoting glucose uptake into cells and storing it as glycogen.

What are the target organs of insulin?

Liver, muscle, and adipose tissue.

What cells produce glucagon?

Alpha (α) cells of the pancreas.

What is the main function of glucagon?

Raises blood glucose levels.

How does glucagon raise blood glucose?

By stimulating glycogen breakdown in the liver.

What is the target organ of glucagon?

Liver