Endocrinology Practice Questions

Q: Primary hypothyroidism is seen in all EXCEPT?

Bexarotene. **Explanation:** The key to this question lies in distinguishing between **Primary** and **Central (Secondary/Tertiary)** hypothyroidism [1]. **Correct Answer: D. Bexarotene** Bexarotene is a selective Retinoid X Receptor (RXR) agonist used in the treatment of cutaneous T-cell lymphoma. It causes **Central Hypothyroidism** by suppressing the thyrotropin ̢-subunit gene expression, leading to a profound suppression of TSH secretion. Unlike primary hypothyroidism, patients on Bexarotene will show low T4 levels with a low or inappropriately normal TSH [1]. **Why the other options are incorrect (Causes of Primary Hypothyroidism):** * **A. Iodine Deficiency:** The most common cause of primary hypothyroidism worldwide. Lack of iodine prevents the synthesis of T3 and T4, leading to a compensatory rise in TSH. * **B. Iodine Excess:** High doses of iodine can inhibit the organification of iodine and the synthesis of thyroid hormones, a phenomenon known as the **Wolff-Chaikoff effect**. While usually transient, it can lead to permanent primary hypothyroidism in patients with underlying thyroid disease. * **C. Lithium:** Lithium inhibits the release of thyroid hormones from the thyroid gland. It is a well-known pharmacological cause of primary hypothyroidism and goiter. **High-Yield Clinical Pearls for NEET-PG:** * **Wolff-Chaikoff Effect:** Autoregulation where excess iodine inhibits thyroid hormone synthesis. * **Jod-Basedow Phenomenon:** Iodine-induced hyperthyroidism (opposite of Wolff-Chaikoff). * **Amiodarone:** A high-yield drug that can cause both hypothyroidism (via Wolff-Chaikoff) and hyperthyroidism (Type 1 and Type 2) [2]. * **TSH Levels:** In Primary Hypothyroidism, TSH is **elevated**. In Central Hypothyroidism (e.g., Bexarotene, Pituitary adenoma), TSH is **low or normal** [1].

Q: A young woman presents with secondary amenorrhea and galactorrhea. MRI shows a pituitary tumor of less than 10 mm diameter. What is the recommended treatment?

Bromocriptine. **Explanation:** The clinical presentation of secondary amenorrhea and galactorrhea in a young woman, combined with an MRI showing a pituitary tumor <10 mm (Microadenoma), is classic for a **Prolactinoma**. [1] **1. Why Bromocriptine is Correct:** Prolactinomas are unique among pituitary tumors because **medical management is the first-line treatment**, regardless of size. [1] Dopamine agonists like **Bromocriptine** or Cabergoline act on D2 receptors in the pituitary to inhibit prolactin secretion and shrink the tumor mass. [1] They effectively restore menses, stop galactorrhea, and achieve tumor shrinkage in over 80% of patients. **2. Why Incorrect Options are Wrong:** * **Hormonal therapy (Option A):** While OCPs can induce withdrawal bleeding, they do not address the underlying hyperprolactinemia or the pituitary tumor. In fact, estrogen can theoretically stimulate lactotroph hyperplasia. * **Radiotherapy (Option B):** This is reserved for refractory cases or aggressive macroadenomas that fail both medical and surgical therapy due to long-term risks like hypopituitarism. * **Chemotherapy (Option C):** Cytotoxic chemotherapy is not used for benign pituitary adenomas. Temozolomide is only considered for rare, malignant pituitary carcinomas. **3. NEET-PG High-Yield Pearls:** * **Drug of Choice:** While Bromocriptine is the traditional answer, **Cabergoline** is now preferred in clinical practice due to higher efficacy and better tolerability (longer half-life). * **Micro vs. Macro:** Microadenomas are <10 mm; Macroadenomas are ≥10 mm. [1] * **Surgery (Transsphenoidal):** Indicated only if the patient is intolerant to dopamine agonists or if the tumor is resistant to medical therapy. * **Hook Effect:** In very large macroadenomas, extremely high prolactin levels can cause a false low reading in lab assays; serial dilution is required for diagnosis.

Q: Hung up reflex is seen in which of the following conditions?

Hypothyroidism. **Explanation:** The **"Hung-up reflex"** (also known as Woltman’s sign) refers to the delayed relaxation phase of a deep tendon reflex, most commonly elicited in the Achilles tendon. **1. Why Hypothyroidism is correct:** In hypothyroidism, there is a generalized slowing of metabolic processes. The delayed relaxation is not due to a defect in the nerve conduction or the initial contraction phase, but rather a **slowing of the calcium reuptake** by the sarcoplasmic reticulum and a decrease in the rate of cross-bridge cycling in skeletal muscle. This results in a characteristic "slow return" of the limb to its neutral position. While "Myxedema" (Option A) is a severe form of hypothyroidism, "Hypothyroidism" is the broader, standard clinical term used in examinations for this sign. **2. Why other options are incorrect:** * **Hyperthyroidism:** This condition presents with **brisk** or hyperactive reflexes (shortened contraction and relaxation phases) due to increased neuromuscular excitability. * **Pheochromocytoma:** This catecholamine-secreting tumor leads to hypertension and tachycardia. While it may cause tremors or hyperreflexia due to sympathetic overactivity, it does not cause a delayed relaxation phase. **3. Clinical Pearls for NEET-PG:** * **Woltman’s Sign:** Another name for the hung-up reflex; it is considered a highly specific clinical sign for hypothyroidism. * **Other causes of delayed relaxation:** Besides hypothyroidism, it can occasionally be seen in pregnancy, diabetes mellitus, hypothermia, and with the use of beta-blockers. * **Muscle involvement in Hypothyroidism:** Look out for **Hoffmann’s Syndrome** (pseudohypertrophy of muscles associated with hypothyroidism in adults) and **Kocher-Debre-Semelaigne Syndrome** (similar presentation in children).

Q: Which of the following is the best marker for diagnosing thyroid-related disorders?

TSH. ### Explanation **Correct Answer: C. TSH** **Why TSH is the best marker:** TSH (Thyroid Stimulating Hormone) is considered the **single best initial screening test** for thyroid dysfunction. This is due to the **inverse logarithmic relationship** between Serum Free T4 and TSH. Even a minute change in the levels of free thyroid hormones (T3/T4) triggers a disproportionately large change in TSH secretion from the anterior pituitary. Consequently, TSH is the most sensitive indicator, often becoming abnormal even when T3 and T4 levels are still within the subclinical (normal) range. **Analysis of Incorrect Options:** * **A & B (T3 and T4):** While these are primary thyroid hormones, they are less sensitive than TSH. Total T3 and T4 levels are often misleading because they are affected by changes in **Thyroxine-Binding Globulin (TBG)** levels (e.g., pregnancy or oral contraceptive use). While Free T4 is useful for confirming diagnosis, it is not the primary screening tool. * **D (Thyroglobulin):** This is a protein produced by follicular cells. It is not used to diagnose hyper- or hypothyroidism. Its primary clinical utility is as a **tumor marker** to monitor for recurrence in patients with differentiated thyroid cancer (papillary or follicular) after total thyroidectomy. **Clinical Pearls for NEET-PG:** * **Primary Hypothyroidism:** High TSH, Low Free T4. * **Primary Hyperthyroidism:** Low (suppressed) TSH, High Free T4. * **Subclinical Disorders:** TSH is abnormal, but Free T4 and Free T3 are within the **normal reference range**. * **Exception:** In **Secondary (Central) Hypothyroidism**, TSH is unreliable (may be low or inappropriately normal); here, Free T4 is the preferred marker for diagnosis and monitoring.

Q: Which of the following medications should not be given to a diabetic patient?

Propranolol. **Explanation:** The correct answer is **Propranolol**. **Why Propranolol is contraindicated:** Propranolol is a non-selective beta-blocker that poses two significant risks to diabetic patients: 1. **Masking Hypoglycemia:** The most critical danger is that it masks the sympathetic "warning signs" of hypoglycemia, such as tachycardia, palpitations, and tremors. A patient may slip into a severe hypoglycemic coma without realizing their blood sugar has dropped. (Note: Sweating is mediated by cholinergic receptors and is usually not masked). 2. **Inhibition of Glycogenolysis:** Beta-2 receptors mediate the breakdown of glycogen into glucose in the liver. By blocking these receptors, Propranolol impairs the body's compensatory mechanism to raise blood glucose levels during a hypoglycemic episode, leading to prolonged and more severe hypoglycemia. **Analysis of Incorrect Options:** * **Theophylline:** A methylxanthine used in asthma/COPD. While it can cause mild hyperglycemia in toxicity, it is not contraindicated in diabetes. * **Digoxin:** A cardiac glycoside used in heart failure and atrial fibrillation. It has no significant effect on glucose metabolism. * **Glyburide:** This is a second-generation Sulfonylurea. It is a standard treatment for Type 2 Diabetes (though used less frequently now due to the risk of hypoglycemia). **NEET-PG High-Yield Pearls:** * If a beta-blocker must be used in a diabetic patient (e.g., post-MI), **Cardioselective (Beta-1) blockers** like Metoprolol or Atenolol are preferred, as they have less effect on glucose metabolism. * **Sweating** is the only sympathetic symptom of hypoglycemia not masked by beta-blockers. * Other drugs causing hyperglycemia: Thiazides, Corticosteroids, and Atypical Antipsychotics (e.g., Olanzapine).

Question 1

Primary hypothyroidism is seen in all EXCEPT?

Accepted Answer

Bexarotene

Answer

Iodine deficiency

Answer

Iodine excess

Answer

Lithium

Question 2

A young woman presents with secondary amenorrhea and galactorrhea. MRI shows a pituitary tumor of less than 10 mm diameter. What is the recommended treatment?

Accepted Answer

Bromocriptine

Answer

Hormonal therapy for withdrawal bleeding

Answer

Radiotherapy

Answer

Chemotherapy

Question 3

Hung up reflex is seen in which of the following conditions?

Accepted Answer

Hypothyroidism

Answer

Myxedema

Answer

Hyperthyroidism

Answer

Pheochromocytoma

Question 4

Which of the following is the best marker for diagnosing thyroid-related disorders?

Accepted Answer

TSH

Answer

T3

Answer

T4

Answer

Thyroglobulin

Question 5

Which of the following medications should not be given to a diabetic patient?

Accepted Answer

Propranolol

Answer

Theophylline

Answer

Digoxin

Answer

Glyburide

Question 6

Which of the following statements is true regarding thyrotoxicosis?

Accepted Answer

In Graves' disease, antibodies are formed against TSH receptors, leading to excessive thyroxine secretion.

Answer

Hashimoto's thyroiditis typically occurs in young males.

Answer

In primary hypothyroidism, decreased TSH levels are observed.

Answer

In Graves' disease, no antibodies are formed against TSH receptors, resulting in decreased thyroxine secretion.

Question 7

Addison disease is commonly associated with which of the following?

Accepted Answer

Autoimmune adrenalitis

Answer

Adrenocortical carcinoma

Answer

Hypernephroma

Answer

Medullary carcinoma of the thyroid

Question 8

A 38-year-old woman presents with new symptoms of palpitations, weight loss, and heat intolerance. On physical examination, she has a mild tremor of her outstretched hands, an enlarged thyroid, and resting tachycardia (heart rate 110/min). Biochemical tests confirm the diagnosis and she is started on methimazole. Which of the following is the most likely mechanism of this drug?

Accepted Answer

Inhibition of thyroidal organic binding and coupling reactions

Answer

Inhibition of iodine uptake

Answer

Lowering serum calcium

Answer

Adrenal suppression

Question 9

Which of the following is NOT typically seen in diabetic ketoacidosis?

Accepted Answer

Normal serum potassium

Answer

Plasma osmolality of 320 mosm/kg

Answer

Urine Rothera test positive

Answer

Urine Benedict's test positive

Question 10

Which of the following causes of gynecomastia is not associated with androgen deficiency?

Accepted Answer

Alcoholic Liver cirrhosis

Answer

Klinefelter's syndrome

Answer

Kallmann syndrome

Answer

Cryptorchidism

Endocrinology — MCQs

Endocrinology — MCQs

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