USMLE Step 1 Endocrine Practice Questions

Which hormone is synthesized in the hypothalamus, stored in the posterior pituitary, and promotes water reabsorption in the kidneys?

• (A) Antidiuretic hormone (ADH / Vasopressin)
• (B) Oxytocin
• (C) Prolactin
• (D) Growth hormone (GH)

What is the primary physiological effect of insulin?

• (A) Lowering blood glucose levels by increasing cellular uptake
• (B) Raising blood glucose levels by stimulating glycogenolysis
• (C) Increasing lipolysis in adipose tissue
• (D) Stimulating gluconeogenesis in the liver

Which hormone, secreted by the adrenal cortex zona glomerulosa, regulates sodium and potassium balance?

• (A) Aldosterone
• (B) Cortisol
• (C) Dehydroepiandrosterone (DHEA)
• (D) Epinephrine

Parathyroid hormone (PTH) increases serum calcium levels by acting on which three target organs?

• (A) Bone, Kidneys, and Intestine (indirectly via Vitamin D)
• (B) Liver, Muscle, and Adipose tissue
• (C) Anterior pituitary, Thyroid, and Adrenal cortex
• (D) Brain, Heart, and Lungs

Which hormone is produced by the alpha cells of the pancreatic islets and generally opposes the actions of insulin?

• (A) Glucagon
• (B) Somatostatin
• (C) Pancreatic polypeptide
• (D) Amylin

Growth hormone (GH) exerts many of its growth-promoting effects indirectly by stimulating the production of what substance, primarily in the liver?

• (A) Insulin-like growth factor 1 (IGF-1 / Somatomedin C)
• (B) Thyroid-stimulating hormone (TSH)
• (C) Adrenocorticotropic hormone (ACTH)
• (D) Erythropoietin (EPO)

What is the primary negative feedback signal regulating the secretion of thyroid-stimulating hormone (TSH) from the anterior pituitary?

• (A) Thyroid hormones (T4 and T3)
• (B) Thyrotropin-releasing hormone (TRH)
• (C) Iodide levels
• (D) Calcitonin

Cortisol, the primary glucocorticoid in humans, is secreted by which zone of the adrenal cortex?

• (A) Zona fasciculata
• (B) Zona glomerulosa
• (C) Zona reticularis
• (D) Adrenal medulla

Which hormone, secreted by the posterior pituitary, stimulates uterine contractions during labor and milk ejection during breastfeeding?

• (A) Oxytocin
• (B) Antidiuretic hormone (ADH)
• (C) Prolactin
• (D) Luteinizing hormone (LH)

What is the mechanism of action of steroid hormones (e.g., cortisol, aldosterone, estrogen, testosterone)?

• (A) Binding to intracellular receptors that regulate gene transcription
• (B) Binding to cell surface receptors coupled to G proteins
• (C) Activating tyrosine kinase receptors
• (D) Opening ligand-gated ion channels

Which condition results from excessive growth hormone (GH) secretion *before* the closure of epiphyseal plates?

• (A) Gigantism
• (B) Acromegaly
• (C) Dwarfism
• (D) Cushing's syndrome

What is the role of 21-hydroxylase in the adrenal cortex?

• (A) Essential enzyme in the synthesis pathways of both cortisol and aldosterone
• (B) Converts cortisol to cortisone
• (C) Synthesizes adrenal androgens
• (D) Inactivates catecholamines

Which hormone is primarily responsible for stimulating spermatogenesis in the seminiferous tubules and synthesis of androgen-binding protein (ABP) by Sertoli cells?

• (A) Follicle-stimulating hormone (FSH)
• (B) Luteinizing hormone (LH)
• (C) Testosterone
• (D) Inhibin B

What is the main physiological stimulus for prolactin release from the anterior pituitary?

• (A) Inhibition by dopamine (prolactin-inhibiting hormone) from the hypothalamus is removed
• (B) Stimulation by Prolactin-releasing hormone (PRH)
• (C) High levels of estrogen
• (D) Low levels of progesterone

A patient presents with heat intolerance, weight loss despite increased appetite, palpitations, anxiety, and a fine tremor. Laboratory tests show high free T4 and T3, and suppressed TSH. Which condition is most likely?

• (A) Hyperthyroidism (e.g., Graves' disease)
• (B) Hypothyroidism (e.g., Hashimoto's thyroiditis)
• (C) Cushing's syndrome
• (D) Addison's disease

Which hormone, produced by the thyroid parafollicular (C) cells, acts to lower serum calcium levels, primarily by inhibiting osteoclast activity?

• (A) Calcitonin
• (B) Parathyroid hormone (PTH)
• (C) Thyroxine (T4)
• (D) Vitamin D (Calcitriol)

Type 1 Diabetes Mellitus is characterized by:

• (A) Autoimmune destruction of pancreatic beta cells leading to absolute insulin deficiency
• (B) Peripheral insulin resistance and relative insulin deficiency
• (C) Excessive glucagon secretion
• (D) Overproduction of cortisol

Which hormone stimulates Leydig cells in the testes to produce testosterone?

• (A) Luteinizing hormone (LH)
• (B) Follicle-stimulating hormone (FSH)
• (C) Gonadotropin-releasing hormone (GnRH)
• (D) Inhibin B

What is the effect of cortisol on blood glucose levels?

• (A) Increases blood glucose levels (diabetogenic effect)
• (B) Decreases blood glucose levels
• (C) Has no effect on blood glucose levels
• (D) Decreases glucose absorption from the gut

Addison's disease (primary adrenal insufficiency) involves destruction of the adrenal cortex. What hormonal changes are expected?

• (A) Low cortisol, low aldosterone, high ACTH
• (B) High cortisol, high aldosterone, low ACTH
• (C) Low cortisol, high aldosterone, low ACTH
• (D) High cortisol, low aldosterone, high ACTH

The conversion of thyroxine (T4) to the more biologically active triiodothyronine (T3) occurs primarily in:

• (A) Peripheral tissues (catalyzed by deiodinases)
• (B) Thyroid follicular cells
• (C) Anterior pituitary
• (D) Hypothalamus

What is the function of Somatostatin secreted by delta cells of the pancreatic islets?

• (A) Inhibits secretion of insulin, glucagon, and pancreatic polypeptide
• (B) Stimulates secretion of insulin and glucagon
• (C) Enhances glucose absorption
• (D) Promotes glycogen synthesis

Which anterior pituitary hormone stimulates the adrenal cortex to produce and release cortisol?

• (A) Adrenocorticotropic hormone (ACTH)
• (B) Thyroid-stimulating hormone (TSH)
• (C) Growth hormone (GH)
• (D) Follicle-stimulating hormone (FSH)

Conn's syndrome (primary hyperaldosteronism) is characterized by excessive aldosterone secretion, typically from an adrenal adenoma. What are the classic laboratory findings?

• (A) Hypertension, hypokalemia, metabolic alkalosis, low renin
• (B) Hypotension, hyperkalemia, metabolic acidosis, high renin
• (C) Hypertension, hyperkalemia, metabolic acidosis, low renin
• (D) Hypotension, hypokalemia, metabolic alkalosis, high renin

During the follicular phase of the menstrual cycle, which hormone is primarily responsible for stimulating the growth and development of ovarian follicles?

• (A) Follicle-stimulating hormone (FSH)
• (B) Luteinizing hormone (LH)
• (C) Estrogen
• (D) Progesterone

The rapid surge of which hormone triggers ovulation and the formation of the corpus luteum?

• (A) Luteinizing hormone (LH)
• (B) Follicle-stimulating hormone (FSH)
• (C) Estrogen
• (D) Progesterone

What is the primary hormone produced by the corpus luteum after ovulation?

• (A) Progesterone
• (B) Estrogen
• (C) Follicle-stimulating hormone (FSH)
• (D) Human chorionic gonadotropin (hCG)

Cushing's syndrome refers to the clinical features resulting from chronic excess of which hormone?

• (A) Cortisol
• (B) Aldosterone
• (C) Testosterone
• (D) Thyroxine (T4)

What is the mechanism of action of metformin, a first-line drug for type 2 diabetes?

• (A) Decreases hepatic glucose production and increases peripheral insulin sensitivity
• (B) Stimulates insulin secretion from pancreatic beta cells
• (C) Slows carbohydrate absorption from the gut
• (D) Increases urinary glucose excretion

Syndrome of Inappropriate ADH Secretion (SIADH) leads to excessive water retention. What are the characteristic laboratory findings?

• (A) Hyponatremia, low serum osmolality, inappropriately concentrated urine (high urine osmolality)
• (B) Hypernatremia, high serum osmolality, dilute urine
• (C) Hyponatremia, high serum osmolality, dilute urine
• (D) Hypernatremia, low serum osmolality, concentrated urine

Which thyroid hormone is more potent and has a shorter half-life?

• (A) Triiodothyronine (T3)
• (B) Thyroxine (T4)
• (C) Reverse T3 (rT3)
• (D) Calcitonin

What is the effect of inhibin B, secreted by Sertoli cells (males) and granulosa cells (females)?

• (A) Selectively inhibits FSH secretion from the anterior pituitary
• (B) Selectively inhibits LH secretion from the anterior pituitary
• (C) Stimulates GnRH release from the hypothalamus
• (D) Enhances the action of testosterone

Pheochromocytoma is a tumor of the adrenal medulla. What substances does it typically secrete in excess?

• (A) Catecholamines (epinephrine, norepinephrine)
• (B) Cortisol and aldosterone
• (C) ACTH
• (D) Thyroid hormones

Which enzyme is responsible for converting testosterone to dihydrotestosterone (DHT) in certain target tissues like the prostate and hair follicles?

• (A) 5-alpha-reductase
• (B) Aromatase
• (C) 17-beta-hydroxysteroid dehydrogenase
• (D) 21-hydroxylase

Hypothyroidism during infancy and early childhood can lead to severe developmental abnormalities known as:

• (A) Cretinism (Congenital Hypothyroidism)
• (B) Graves' disease
• (C) Rickets
• (D) Turner syndrome

Which hormone promotes gluconeogenesis, lipolysis, and protein catabolism, and also suppresses the immune system?

• (A) Cortisol
• (B) Insulin
• (C) Glucagon
• (D) Growth Hormone

What is the function of aromatase, an enzyme found in adipose tissue, gonads, and brain?

• (A) Converts androgens (e.g., testosterone) to estrogens (e.g., estradiol)
• (B) Converts estrogens to androgens
• (C) Synthesizes aldosterone
• (D) Activates Vitamin D

Acromegaly results from excessive growth hormone (GH) secretion starting *after* the closure of epiphyseal plates. What are its characteristic features?

• (A) Enlargement of hands, feet, and facial bones; organomegaly; metabolic dysfunction
• (B) Excessive linear height
• (C) Delayed puberty
• (D) Hypoglycemia and muscle wasting

What is the Wolff-Chaikoff effect?

• (A) Excess iodide temporarily inhibits thyroid hormone synthesis and release
• (B) Low iodide stimulates thyroid hormone synthesis
• (C) TSH stimulation causes thyroid gland hypertrophy
• (D) Autoantibodies stimulate the TSH receptor

Multiple Endocrine Neoplasia Type 1 (MEN1) is characterized by tumors in which three endocrine glands ('3 Ps')?

• (A) Parathyroid, Pancreatic islet cells, Pituitary (anterior)
• (B) Pheochromocytoma, Parathyroid, Pituitary
• (C) Thyroid (medullary carcinoma), Pheochromocytoma, Parathyroid
• (D) Pancreas, Pituitary, Pineal