Endocrinology Practice Questions

Q: A 65-year-old woman presents with low mood. Her past medical history includes atrial fibrillation and type 2 diabetes. Clinical examination reveals cool peripheries and a pulse of 45 bpm. Thyroid function tests show TSH: 6.5 mU/L and T4: 4 pmol/L. Which of the following is the most likely cause of this patient's symptoms?

Drug-induced hypothyroidism. ### Explanation **1. Why Drug-induced Hypothyroidism is correct:** The patient presents with classic symptoms of hypothyroidism (low mood, cool peripheries, bradycardia) and biochemical evidence of primary hypothyroidism (High TSH, Low T4). The crucial clue lies in her history of **atrial fibrillation**. **Amiodarone**, a commonly used Class III antiarrhythmic for AFib, contains 37% iodine by weight. It can induce hypothyroidism via the **Wolff-Chaikoff effect** (excess iodine inhibiting thyroid hormone synthesis) [1]. Given the clinical context of AFib, amiodarone-induced hypothyroidism is the most likely diagnosis [1]. **2. Why the other options are incorrect:** * **Hashimoto’s Thyroiditis:** While the most common cause of primary hypothyroidism, it typically presents with much higher TSH levels (often >10 mU/L) and wouldn't specifically link to a history of atrial fibrillation as strongly as a drug-induced cause in this scenario. * **Secondary/Tertiary Hypothyroidism:** These refer to central hypothyroidism (pituitary or hypothalamic failure). In these cases, the **TSH would be low or inappropriately normal** in the presence of a low T4. This patient has an elevated TSH (6.5 mU/L), which localizes the pathology to the thyroid gland itself (Primary). **3. NEET-PG High-Yield Pearls:** * **Amiodarone & Thyroid:** It can cause both hypothyroidism (Wolff-Chaikoff) and hyperthyroidism (Jod-Basedow effect or destructive thyroiditis) [1]. * **Wolff-Chaikoff Effect:** A protective autoregulatory phenomenon where high iodine levels inhibit thyroperoxidase, decreasing T3/T4 production. * **Lithium:** Another high-yield drug causing hypothyroidism by inhibiting thyroid hormone release. * **Subclinical Hypothyroidism:** Defined as elevated TSH with **normal** T4. This patient has **overt** hypothyroidism because her T4 is low.

Q: SIADH secretion is seen in all except:

Interstitial Nephritis. **Explanation:** The Syndrome of Inappropriate Antidiuretic Hormone (SIADH) is characterized by the excessive release of ADH, leading to water retention and dilutional hyponatremia [1], [2]. **Why Interstitial Nephritis is the correct answer:** Interstitial nephritis is a cause of **Nephrogenic Diabetes Insipidus (NDI)**, not SIADH [3]. In NDI, the renal tubules become resistant to the action of ADH [3]. This results in the inability to concentrate urine, leading to polyuria and hypernatremia—the physiological opposite of SIADH. **Analysis of Incorrect Options:** * **Lung Abscess:** Pulmonary pathologies (pneumonia, abscess, tuberculosis) are classic triggers for SIADH. * **Vinca Alkaloids:** Drugs like Vincristine and Vinblastine are well-known causes of SIADH. They exert a direct neurotoxic effect on the hypothalamus and neurohypophyseal tract, leading to unregulated ADH release. * **Bronchial Adenoma:** Ectopic ADH production is a hallmark of certain tumors. While Small Cell Lung Cancer (SCLC) is the most common, bronchial adenomas (carcinoid tumors) can also secrete ADH autonomously. **NEET-PG High-Yield Pearls:** 1. **Diagnosis:** SIADH is a diagnosis of exclusion. Key features: Euvolemic hyponatremia, low serum osmolality ( 100 mOsm/kg) [1]. 2. **Drug Causes (Mnemonic: "S-C-V"):** **S**SRIs, **C**arbamazepine/Cyclophosphamide, and **V**inca alkaloids. 3. **Treatment:** Fluid restriction is the first-line treatment. For severe symptoms, use hypertonic saline (3%). **Vaptans** (Tolvaptan) are vasopressin receptor antagonists used in chronic cases. 4. **Caution:** Rapid correction of hyponatremia can lead to **Osmotic Demyelination Syndrome** (Central Pontine Myelinolysis). Keep correction <8–10 mmol/L in 24 hours.

Q: 11-hydroxylase deficiency leads to which of the following?

Hypertension. **Explanation:** Congenital Adrenal Hyperplasia (CAH) due to **11β-hydroxylase deficiency** is the second most common cause of CAH. Understanding the steroid biosynthesis pathway is key to solving this [1]: 1. **Why Hypertension is Correct:** 11β-hydroxylase is responsible for converting **11-deoxycorticosterone (DOC)** to corticosterone and **11-deoxycortisol** to cortisol. When this enzyme is deficient, there is a buildup of 11-deoxycorticosterone (DOC) [1]. DOC is a potent mineralocorticoid [2]. Its accumulation leads to sodium and water retention and potassium excretion, resulting in **hypertension** and hypokalemia. This distinguishes it from 21-hydroxylase deficiency, which presents with hypotension (salt-wasting). 2. **Why other options are incorrect:** * **Hypotension:** This occurs in 21-hydroxylase deficiency due to the lack of mineralocorticoids (aldosterone). In 11β-hydroxylase deficiency, the excess DOC prevents hypotension. * **Hypoglycemia:** While cortisol (a glucocorticoid) is low, the clinical hallmark of 11β-hydroxylase deficiency is the mineralocorticoid excess effect (hypertension) and androgen excess. * **Normal Puberty:** This is incorrect because the "shunting" of precursors leads to **excess adrenal androgens**. This causes virilization in females (ambiguous genitalia) and precocious pseudopoterty in males. **High-Yield Clinical Pearls for NEET-PG:** * **The "Rule of 1s":** If the enzyme starts with **1** (11β-hydroxylase, 17α-hydroxylase), it causes **Hypertension**. * **Virilization:** Both 21 and 11β-hydroxylase deficiencies cause virilization (increased androgens), whereas 17α-hydroxylase deficiency causes delayed puberty/sexual infantilism. * **Biochemical Marker:** Elevated levels of **11-deoxycortisol** and **S-androstenedione** are diagnostic for 11β-hydroxylase deficiency.

Q: Which of the following conditions is associated with pituitary adenoma?

Multiple Endocrine Neoplasia type 4 (MEN4). **Explanation:** The correct answer is **Multiple Endocrine Neoplasia type 4 (MEN4)**. **1. Why MEN4 is correct:** MEN4 is a rare autosomal dominant syndrome caused by a germline mutation in the **CDKN1B gene** (encoding the p27 protein), which acts as a cyclin-dependent kinase inhibitor. Clinically, MEN4 presents very similarly to MEN1. It is characterized by a "3P" pattern, though with lower penetrance: **Pituitary adenomas**, **Parathyroid adenomas**, and **Pancreatic neuroendocrine tumors**. Therefore, pituitary adenoma is a hallmark feature of this condition. **2. Why the other options are incorrect:** * **MEN2A:** Caused by **RET proto-oncogene** mutations. It is characterized by the "MPH" triad: Medullary thyroid carcinoma (MTC), Pheochromocytoma, and Hyperparathyroidism. It does **not** involve the pituitary gland. * **MEN2B (formerly MEN3):** Also caused by RET mutations. It presents with MTC, Pheochromocytoma, and mucosal neuromas/Marfanoid habitus. Pituitary adenomas are not part of this syndrome. * **MEN3:** This is an older nomenclature for MEN2B and is no longer used as a separate category in modern classification. **3. NEET-PG High-Yield Pearls:** * **MEN1 (Wermer Syndrome):** The classic "3Ps" (Pituitary, Parathyroid, Pancreas). Caused by the *MEN1* gene (Menin). * **MEN4:** Think of it as "MEN1-like" but caused by *CDKN1B*. * **Pituitary involvement:** Only seen in **MEN1** and **MEN4**. * **Medullary Thyroid Carcinoma:** Present in 100% of MEN2A and 2B cases; prophylactic thyroidectomy is often indicated. * **Most common pituitary tumor in MEN1/4:** Prolactinoma.

Q: Which of the following could develop with a mucosal neuroma on the lower lip, a family history of medullary thyroid carcinoma, and recent introduction of severe headaches, perspiration, palpitations, and hypertension?

Pheochromocytoma. ### Explanation The clinical presentation described is classic for **Multiple Endocrine Neoplasia Type 2B (MEN 2B)**. This autosomal dominant syndrome, caused by a mutation in the **RET proto-oncogene**, is characterized by a triad of: 1. **Medullary Thyroid Carcinoma (MTC):** Often aggressive and occurs early in life (explaining the family history). 2. **Pheochromocytoma:** Occurs in approximately 50% of cases. 3. **Mucosal Neuromas:** Typically found on the tongue, lips (as seen here), and eyelids, often accompanied by a **Marfanoid habitus**. The patient’s "recent introduction" of severe headaches, perspiration, palpitations, and hypertension forms the classic **"PHE" triad** (Palpitations, Headache, Episodic sweating), which is pathognomonic for a **Pheochromocytoma** (Option D). #### Analysis of Incorrect Options: * **A & B (Gastrinoma/Insulinoma):** These are Pancreatic Neuroendocrine Tumors (NETs) [1], which are components of **MEN 1** (the "3 Ps": Pituitary, Parathyroid, Pancreas), not MEN 2B. Insulinomas are confirmed as a pancreatic NET associated with hormone excess syndromes [3]. * **C (Parathyroid Adenoma):** While parathyroid hyperplasia/adenoma is a key feature of **MEN 1** and **MEN 2A**, it is characteristically **characteristically absent** in MEN 2B. #### NEET-PG High-Yield Pearls: * **MEN 2A (Sipple Syndrome):** MTC + Pheochromocytoma + Parathyroid Hyperplasia. * **MEN 2B (Wagenmann–Froboese Syndrome):** MTC + Pheochromocytoma + Mucosal Neuromas/Marfanoid habitus. * **Rule of 10s for Pheochromocytoma:** 10% bilateral, 10% malignant, 10% extra-adrenal, 10% pediatric, and 10% familial [2]. * **Clinical Priority:** In any MEN 2 patient, always screen for and surgically remove a Pheochromocytoma **before** addressing the thyroid to prevent a lethal hypertensive crisis during anesthesia [2].

Q: Which of the following is NOT associated with adrenal insufficiency?

Metabolic alkalosis. **Explanation:** Adrenal insufficiency (specifically primary adrenal insufficiency or Addison’s disease) results from the deficiency of adrenal cortical hormones: **Aldosterone, Cortisol, and Androgens.** [1] **Why Metabolic Alkalosis is the Correct Answer:** Adrenal insufficiency is characterized by **Metabolic Acidosis** (specifically Normal Anion Gap Metabolic Acidosis), not alkalosis. Aldosterone normally acts on the distal convoluted tubules to reabsorb sodium and excrete potassium and hydrogen ions ($H^+$). [1] In its absence, $H^+$ ions are retained in the blood, leading to acidosis. Metabolic alkalosis is instead associated with conditions of mineralocorticoid excess like Conn's syndrome. [2] **Analysis of Incorrect Options:** * **A. Hyponatremia:** Aldosterone deficiency leads to "salt wasting" (loss of $Na^+$ in urine). Additionally, cortisol deficiency increases ADH secretion, causing water retention and dilutional hyponatremia. * **B. Hyperkalemia:** Without aldosterone, the kidneys cannot effectively secrete potassium into the urine, leading to elevated serum potassium levels. [1] * **C. Hypoglycemia:** Cortisol is a counter-regulatory hormone that promotes gluconeogenesis and antagonizes insulin. Its absence leads to impaired glucose production and increased insulin sensitivity. **High-Yield Clinical Pearls for NEET-PG:** * **Primary vs. Secondary:** Hyponatremia occurs in both, but **Hyperkalemia** is seen *only* in Primary Adrenal Insufficiency (because aldosterone is regulated by the RAAS, which remains intact in secondary/pituitary causes). * **Hyperpigmentation:** Seen only in Primary Adrenal Insufficiency due to increased ACTH and POMC levels (stimulating melanocytes). * **Cosyntropin Stimulation Test:** The gold standard for diagnosis. * **Acute Crisis Management:** Immediate IV fluids (Normal Saline) and IV Hydrocortisone. Do not wait for lab confirmation if a crisis is suspected.

Q: Which of the following is NOT a cause of Gynaecomastia?

Hypothyroidism. Gynaecomastia is the benign proliferation of glandular breast tissue in males, primarily caused by an imbalance between estrogen and androgen action. **Why Hypothyroidism is the correct answer:** While **Hyperthyroidism** is a well-known cause of gynaecomastia (due to increased Sex Hormone Binding Globulin (SHBG) levels which lower free testosterone and increase peripheral aromatization), **Hypothyroidism** is generally not associated with it. In fact, primary hypothyroidism in prepubertal boys may cause precocious puberty, but it does not typically cause gynaecomastia in adults. **Analysis of Incorrect Options:** * **Kallmann Syndrome:** This is a form of hypogonadotropic hypogonadism (GnRH deficiency). Low levels of testosterone lead to an increased estrogen-to-androgen ratio, resulting in gynaecomastia. * **Obesity:** Adipose tissue contains the enzyme **aromatase**, which converts androgens (androstenedione and testosterone) into estrogens (estrone and estradiol) [1]. Increased fat mass leads to higher systemic estrogen levels. * **Klinefelter Syndrome (47, XXY):** This is the most common genetic cause of male hypogonadism [2]. It features primary testicular failure (low testosterone) and elevated gonadotropins (LH/FSH). The high LH stimulates Leydig cell aromatase, significantly increasing estrogen production. **NEET-PG High-Yield Pearls:** * **Physiological Gynaecomastia:** Occurs in three peaks: Neonatal (maternal estrogens), Pubertal (transient imbalance), and Senile (declining testosterone) [1]. * **Drug-induced Gynaecomastia (Mnemonic: DISCO):** **D**igoxin, **I**soniazid, **S**pironolactone (most common), **C**imetidine, **O**estrogens/Ketoconazole. * **Clinical Distinction:** True gynaecomastia (glandular tissue) must be differentiated from **pseudogynaecomastia** (fat deposition seen in obesity) by palpation [1].

Q: A 20-year-old male presents with chronic constipation, headache, and palpitations. On examination, he has Marfanoid habitus, neuromas of the tongue, medullated corneal nerve fibers, and a 2 x 2 cm nodule in the right lobe of the thyroid. This patient is a case of -

Multiple Endocrine Neoplasia (MEN) IIB. ### Explanation The patient presents with a classic constellation of symptoms diagnostic of **Multiple Endocrine Neoplasia Type 2B (MEN 2B)**. **Why Option D is Correct:** MEN 2B is characterized by the triad of **Medullary Thyroid Carcinoma (MTC)**, **Pheochromocytoma**, and **Mucosal Neuromas**. * **Marfanoid Habitus:** Unlike MEN 2A, patients with MEN 2B often exhibit a thin body habitus with long limbs and joint laxity. * **Mucosal Neuromas:** The "neuromas of the tongue" and "medullated corneal nerve fibers" are pathognomonic features of MEN 2B. * **Pheochromocytoma:** The symptoms of headache and palpitations suggest an underlying catecholamine-secreting tumor. * **MTC:** The thyroid nodule represents MTC, which is more aggressive and occurs earlier in MEN 2B than in other forms. **Why Other Options are Incorrect:** * **Option A & B:** While MTC is present, these options do not account for the extra-thyroidal manifestations like mucosal neuromas and Marfanoid habitus. * **Option C (MEN 2A):** While MEN 2A also features MTC and Pheochromocytoma, it is associated with **Primary Hyperparathyroidism** rather than mucosal neuromas or Marfanoid habitus. **High-Yield Clinical Pearls for NEET-PG:** 1. **Genetics:** Both MEN 2A and 2B are caused by germline mutations in the **RET proto-oncogene** (Chromosome 10). 2. **MTC Screening:** In MEN 2B, MTC is highly aggressive; prophylactic thyroidectomy is often recommended within the **first year of life**. 3. **Gastrointestinal Involvement:** Chronic constipation in these patients can be due to **intestinal ganglioneuromatosis**, a common feature of MEN 2B. 4. **Rule of Thumb:** If you see "Mucosal Neuromas" or "Marfanoid Habitus" in a thyroid case, think **MEN 2B**.

Question 1

A 65-year-old woman presents with low mood. Her past medical history includes atrial fibrillation and type 2 diabetes. Clinical examination reveals cool peripheries and a pulse of 45 bpm. Thyroid function tests show TSH: 6.5 mU/L and T4: 4 pmol/L. Which of the following is the most likely cause of this patient's symptoms?

Accepted Answer

Drug-induced hypothyroidism

Answer

Hashimoto's thyroiditis

Answer

Secondary hypothyroidism

Answer

Tertiary hypothyroidism

Question 2

A 25-year-old young lady presented with a complaint of acute hirsutism and hoarseness of voice. Which of the following is the best investigation for diagnosis?

Accepted Answer

Blood DHEA levels

Answer

Blood pregnenolone levels

Answer

17-ketosteroids level

Answer

LH and FSH levels

Question 3

SIADH secretion is seen in all except:

Accepted Answer

Interstitial Nephritis

Answer

Lung abscess

Answer

Vinka alkaloids

Answer

Bronchial adenoma

Question 4

11-hydroxylase deficiency leads to which of the following?

Accepted Answer

Hypertension

Answer

Hypotension

Answer

Hypoglycemia

Answer

Normal puberty

Question 5

Which of the following conditions is associated with pituitary adenoma?

Accepted Answer

Multiple Endocrine Neoplasia type 4 (MEN4)

Answer

Multiple Endocrine Neoplasia type 2A (MEN2A)

Answer

Multiple Endocrine Neoplasia type 2B (MEN2B)

Answer

Multiple Endocrine Neoplasia type 3 (MEN3)

Question 6

Which of the following could develop with a mucosal neuroma on the lower lip, a family history of medullary thyroid carcinoma, and recent introduction of severe headaches, perspiration, palpitations, and hypertension?

Accepted Answer

Pheochromocytoma

Answer

Gastrinoma

Answer

Insulinoma

Answer

Parathyroid adenoma

Question 7

Which of the following is NOT associated with adrenal insufficiency?

Accepted Answer

Metabolic alkalosis

Answer

Hyponatremia

Answer

Hyperkalemia

Answer

Hypoglycemia

Question 8

Brown tumors, compression syndromes, and erythropoietin resistance are seen in which condition?

Accepted Answer

Hyperparathyroidism

Answer

Hypothyroidism

Answer

Hyperthyroidism

Answer

Osteoporosis

Question 9

Which of the following is NOT a cause of Gynaecomastia?

Accepted Answer

Hypothyroidism

Answer

Kallmann syndrome

Answer

Obesity

Answer

Klinefelter syndrome

Question 10

A 20-year-old male presents with chronic constipation, headache, and palpitations. On examination, he has Marfanoid habitus, neuromas of the tongue, medullated corneal nerve fibers, and a 2 x 2 cm nodule in the right lobe of the thyroid. This patient is a case of -

Accepted Answer

Multiple Endocrine Neoplasia (MEN) IIB

Answer

Sporadic medullary carcinoma of the thyroid

Answer

Familial medullary carcinoma of the thyroid

Answer

Multiple Endocrine Neoplasia (MEN) IIA

Endocrinology — MCQs

Endocrinology — MCQs

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