Endocrinology Practice Questions

Q: Insulin release is inhibited by:

Somatostatin. ### Explanation **Correct Answer: A. Somatostatin** **Mechanism of Action:** Insulin secretion from the pancreatic **Beta cells** is regulated by a complex interplay of nutrients, hormones, and neural inputs. **Somatostatin**, secreted by the **Delta ($\delta$) cells** of the pancreas, acts as a potent universal inhibitor. It exerts a paracrine effect on neighboring Beta cells by binding to **SSTR-5 receptors**, which are coupled to inhibitory G-proteins ($G_i$). This leads to a decrease in intracellular cAMP and the inhibition of calcium influx, effectively shutting down insulin release. **Analysis of Incorrect Options:** * **B. Glucagon:** Secreted by Alpha cells, glucagon actually **stimulates** insulin release. This paracrine interaction ensures that as glucagon raises blood glucose, insulin is available to facilitate glucose uptake by peripheral tissues. * **C. Acetylcholine:** This is the primary neurotransmitter of the parasympathetic nervous system (Vagus nerve). It **stimulates** insulin secretion (via $M_3$ receptors) in anticipation of nutrient absorption during the "rest and digest" phase. * **D. Amino Acids:** Arginine and Lysine are potent **secretagogues** for insulin. Their presence signals a fed state, necessitating insulin for protein synthesis and glucose regulation. **High-Yield NEET-PG Pearls:** * **Most potent stimulator:** Glucose is the primary physiological stimulus for insulin. * **Incretin Effect:** Oral glucose causes a greater insulin response than IV glucose due to hormones like **GLP-1 and GIP**. * **Adrenergic Control:** $\alpha_2$-adrenergic stimulation **inhibits** insulin (dominant during stress/exercise), while $\beta_2$-stimulation **increases** it. * **Biphasic Release:** Insulin is released in two phases; the first phase is the release of pre-formed granules, and the second is the synthesis of new insulin.

Q: If a normal individual receives an insulin injection that lowers plasma glucose to 30 mg/dl, which of the following hormones will not be released?

Aldosterone. **Explanation:** The physiological response to hypoglycemia (plasma glucose <70 mg/dl) involves the activation of the **Counter-regulatory Hormone System**. This system aims to restore glucose levels through glycogenolysis and gluconeogenesis. **Why Aldosterone is the Correct Answer:** Aldosterone is a mineralocorticoid primarily regulated by the **Renin-Angiotensin-Aldosterone System (RAAS)** in response to low blood pressure or hypovolemia, and by serum **Potassium ($K^+$)** levels. It is not a counter-regulatory hormone. Hypoglycemia does not trigger the RAAS or significant electrolyte shifts that would necessitate aldosterone release. **Why the other options are incorrect:** * **ACTH (Option A):** Hypoglycemia is a potent stressor that activates the Hypothalamic-Pituitary-Adrenal (HPA) axis. The hypothalamus releases CRH, which stimulates the anterior pituitary to release **ACTH**, subsequently increasing **Cortisol**. Cortisol promotes gluconeogenesis. * **Epinephrine (Option B):** This is the "first line" rapid response to hypoglycemia. Low glucose triggers the sympathetic nervous system and the adrenal medulla to release epinephrine, which immediately stimulates hepatic glycogenolysis. * **Growth Hormone (Option C):** GH is released in response to hypoglycemia to decrease peripheral glucose utilization and promote lipolysis, acting as a glucose-sparing agent. **High-Yield NEET-PG Pearls:** 1. **Hierarchy of Response:** The first defense against hypoglycemia is the suppression of endogenous insulin, followed by a rise in **Glucagon** and **Epinephrine**. 2. **Insulin Tolerance Test (ITT):** Inducing hypoglycemia with insulin is the "Gold Standard" test to evaluate the integrity of the HPA axis and Growth Hormone reserve. 3. **Glucagon vs. Epinephrine:** Glucagon is the most important hormone for acute recovery from hypoglycemia in non-diabetics; however, if glucagon is deficient, epinephrine becomes critical.

Q: Cutting of the pituitary stalk decreases all of the following hormones except?

Prolactin. The secretion of anterior pituitary hormones is primarily regulated by the hypothalamus via the **hypothalamic-hypophyseal portal system**. Most anterior pituitary hormones (ACTH, TSH, growth hormone, FSH, LH) are under **stimulatory** control by hypothalamic releasing factors [1]. However, **Prolactin** is the unique exception; it is under tonic **inhibitory** control by **Dopamine** [3]. When the pituitary stalk is severed (Pituitary Stalk Interruption), the connection between the hypothalamus and the pituitary is lost. This results in: 1. **Decreased levels** of hormones that require hypothalamic stimulation (ACTH, GH, FSH, LH, and TSH). 2. **Increased levels** of Prolactin, because the inhibitory influence of Dopamine is removed [3]. This phenomenon is often referred to as "Stalk Effect" hyperprolactinemia. **Analysis of Options:** * **A, B, and D (ACTH, GH, FSH):** These are incorrect because their secretion depends on CRH, GHRH, and GnRH, respectively. Cutting the stalk prevents these releasing hormones from reaching the anterior pituitary, leading to a deficiency [4]. * **C (Prolactin):** This is the correct answer because its levels **increase** rather than decrease when the inhibitory dopaminergic pathway is disrupted. **High-Yield Clinical Pearls for NEET-PG:** * **Dopamine = Prolactin Inhibiting Factor:** Any drug that blocks dopamine (e.g., antipsychotics like Haloperidol or prokinetics like Metoclopramide) will cause hyperprolactinemia. * **Stalk Effect vs. Prolactinoma:** In stalk compression (e.g., by a Craniopharyngioma), prolactin levels are usually 200 ng/mL strongly suggest a Prolactinoma. * **Posterior Pituitary:** Stalk transection also leads to **Diabetes Insipidus** because ADH (Vasopressin) and Oxytocin, synthesized in the hypothalamus, can no longer be transported to the posterior pituitary for release [2].

Q: Which of the following statements regarding prolactin levels is TRUE?

Highest during pregnancy and fall during lactation. **Explanation:** **Understanding Prolactin Dynamics** The correct answer is **B**. During pregnancy, prolactin levels rise progressively, reaching their peak (up to 10–20 times non-pregnant levels) at term. This increase is driven by high levels of circulating **estrogen**, which stimulates the lactotrophs in the anterior pituitary to undergo hyperplasia and hypertrophy. Post-delivery, estrogen levels plummet. In non-breastfeeding women, prolactin returns to baseline within 2–3 weeks. In breastfeeding women, while basal prolactin remains elevated, it gradually **falls** over several months of lactation, though it spikes transiently during each episode of suckling (the neuroendocrine reflex). **Analysis of Incorrect Options:** * **Option A:** Incorrect. Prolactin is at its highest during pregnancy, not lowest. It does not increase *after* delivery; rather, the *action* of prolactin (lactogenesis) begins after delivery once the inhibitory effect of progesterone is removed. * **Option C:** Incorrect. Both pregnancy and lactation are the primary physiological states that significantly alter prolactin secretion. * **Option D:** Incorrect. Prolactin follows a highly predictable physiological pattern in all normal pregnancies. **High-Yield Clinical Pearls for NEET-PG:** * **The Progesterone Paradox:** Even though prolactin is high during pregnancy, milk secretion is inhibited by high **Progesterone** levels. Lactation only begins after the placenta is delivered and progesterone levels drop. * **Amniotic Fluid:** Prolactin is found in high concentrations in amniotic fluid, where it aids in fetal osmoregulation. * **Lactational Amenorrhea:** High prolactin inhibits **GnRH pulsatility**, leading to suppressed FSH/LH and subsequent anovulation. * **Drug of Choice:** For pathological hyperprolactinemia (Prolactinoma), the drug of choice is **Cabergoline** (a dopamine agonist).

Q: Which of the following hormonal concentrations decreases with age?

Growth hormone. **Explanation:** The correct answer is **Growth Hormone (GH)**. This phenomenon is known as **somatopause**. GH secretion peaks during puberty and undergoes a progressive decline starting in the third decade of life (approximately 14% decrease per decade). This decline is primarily due to decreased hypothalamic GHRH secretion and increased somatostatin tone, contributing to age-related changes like decreased muscle mass (sarcopenia) and increased visceral fat. **Analysis of Options:** * **A. Parathormone (PTH):** PTH levels typically **increase** with age. This is often a secondary response to declining Vitamin D levels, reduced calcium absorption in the gut, and declining renal function in the elderly. * **B. FSH (Follicle-Stimulating Hormone):** FSH levels **increase** significantly with age, particularly in females during menopause. As ovarian follicles deplete, the loss of negative feedback from estrogen and inhibin leads to a compensatory rise in FSH and LH. * **D. Norepinephrine:** Plasma levels of norepinephrine generally **increase** with age due to increased sympathetic nervous system activity and reduced clearance from the synaptic cleft. **High-Yield NEET-PG Pearls:** * **Hormones that Decrease with Age:** Growth Hormone, Melatonin, DHEA (Dehydroepiandrosterone), Testosterone, and Estrogen. * **Hormones that Increase with Age:** PTH, FSH, LH, Norepinephrine, and Vasopressin (ADH). * **Hormones that remain relatively Constant:** Thyroid hormones (T3/T4) and Cortisol (though the circadian rhythm of cortisol may flatten). * **Somatopause Clinical Correlation:** The decline in GH/IGF-1 axis is a major contributor to the "frailty syndrome" in the elderly.

Q: Which of the following is NOT an endocrine function associated with the kidney?

Natriuretic peptide secretion. The kidney is a vital endocrine organ, but it is not the primary source of natriuretic peptides. ### **Why Option B is Correct** **Natriuretic peptides** (specifically ANP and BNP) are primarily secreted by the **heart**. Atrial Natriuretic Peptide (ANP) is secreted by the atrial myocytes, and Brain Natriuretic Peptide (BNP) is secreted by ventricular myocytes in response to stretch (volume overload). While the kidney is the *target* organ for these peptides (where they promote sodium excretion), it does not secrete them. ### **Why Other Options are Incorrect** * **A. Erythropoietin (EPO):** Approximately 90% of EPO is synthesized by the **peritubular interstitial cells** of the renal cortex in response to hypoxia. It stimulates RBC production in the bone marrow. * **C. 1,25-dihydroxycholecalciferol (Calcitriol):** The kidney performs the final, rate-limiting step of Vitamin D activation. The enzyme **1-alpha-hydroxylase** (located in the proximal convoluted tubule) converts 25-hydroxyvitamin D into the active form, Calcitriol. * **D. Renin:** Renin is secreted by the **Juxtaglomerular (JG) cells** of the afferent arteriole. It is the initiating enzyme of the Renin-Angiotensin-Aldosterone System (RAAS), crucial for blood pressure regulation. ### **High-Yield NEET-PG Pearls** * **Urodilatin:** A rare natriuretic peptide that *is* produced by the distal tubule, but "Natriuretic Peptide" as a general term refers to the cardiac hormones ANP/BNP. * **Chronic Kidney Disease (CKD):** Patients develop anemia primarily due to **EPO deficiency** and secondary hyperparathyroidism due to **Calcitriol deficiency**. * **Prostaglandins:** The kidney also produces PGE2 and PGI2, which act as local vasodilators to maintain renal blood flow.

Q: Sex hormone-binding globulin (SHBG) levels are decreased in which of the following conditions?

Increased androgen levels. **Explanation:** Sex hormone-binding globulin (SHBG) is a glycoprotein produced primarily by the **liver**. It binds to sex steroids (testosterone, DHT, and estradiol) to regulate their bioavailability; only the "free" hormone is biologically active. **Why Option B is Correct:** The synthesis of SHBG in the liver is inhibited by **androgens, insulin, and obesity**. Therefore, in conditions with increased androgen levels (such as PCOS or androgen-secreting tumors), SHBG levels decrease. This creates a clinical "vicious cycle": lower SHBG leads to higher levels of free (active) testosterone, further worsening androgenic symptoms like hirsutism. **Why Other Options are Incorrect:** * **A. Hyperthyroidism:** Thyroid hormones (T3/T4) **stimulate** the hepatic production of SHBG. Thus, SHBG levels are elevated in hyperthyroidism. * **C. Increased Estrogen levels:** Estrogen is a potent stimulator of SHBG synthesis. High estrogen levels increase SHBG, which is why women generally have higher levels than men. * **D. Pregnancy:** This is a state of high endogenous estrogen production, which significantly **increases** SHBG levels (often 5–10 fold). **High-Yield Clinical Pearls for NEET-PG:** * **SHBG Increases in:** Hyperthyroidism, Pregnancy, Oral Contraceptive Pill (OCP) use, Cirrhosis, and Aging (in men). * **SHBG Decreases in:** Hypothyroidism, Obesity, PCOS, Hyperinsulinemia/Type 2 Diabetes, and Acromegaly. * **Clinical Correlation:** In **PCOS**, the combination of high androgens and hyperinsulinemia synergistically suppresses SHBG, making it a key marker for the disease.

Question 1

Insulin release is inhibited by:

Accepted Answer

Somatostatin

Answer

Glucagon

Answer

Acetylcholine

Answer

Amino acids

Question 2

If a normal individual receives an insulin injection that lowers plasma glucose to 30 mg/dl, which of the following hormones will not be released?

Accepted Answer

Aldosterone

Answer

ACTH

Answer

Epinephrine

Answer

Growth hormone

Question 3

Cutting of the pituitary stalk decreases all of the following hormones except?

Accepted Answer

Prolactin

Answer

ACTH

Answer

GH

Answer

FSH

Question 4

Which of the following receptor genes controls TSH secretion?

Accepted Answer

TR beta 2

Answer

TR alpha 1

Answer

TR alpha 2

Answer

TR beta 1

Question 5

Which of the following is responsible for fasting hypoglycemia?

Accepted Answer

Increased insulin level

Answer

Decreased insulin level

Answer

Increased glycogen

Answer

Increased glucagon in the liver

Question 6

Which of the following statements regarding prolactin levels is TRUE?

Accepted Answer

Highest during pregnancy and fall during lactation

Answer

Lowest in pregnancy and increases after delivery

Answer

Unaffected by pregnancy and lactation

Answer

Variable in every pregnancy

Question 7

Which of the following hormonal concentrations decreases with age?

Accepted Answer

Growth hormone

Answer

Parathormone

Answer

FSH

Answer

Norepinephrine

Question 8

All of the following statements about adrenal glands are true EXCEPT:

Accepted Answer

The adrenal medulla normally secretes epinephrine in excess of norepinephrine.

Answer

Chromaffin granules are seen in pheochromocytoma.

Answer

Tumors of the adrenal medulla secrete epinephrine in excess of norepinephrine.

Answer

The adrenal medulla is not essential for life.

Question 9

Which of the following is NOT an endocrine function associated with the kidney?

Accepted Answer

Natriuretic peptide secretion

Answer

Erythropoietin secretion

Answer

1,25-dihydroxycholecalciferol formation

Answer

Renin secretion

Question 10

Sex hormone-binding globulin (SHBG) levels are decreased in which of the following conditions?

Accepted Answer

Increased androgen levels

Answer

Hyperthyroidism

Answer

Increased estrogen levels

Answer

Pregnancy

Endocrinology — MCQs

Endocrinology — MCQs

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