Endocrinology Practice Questions

Q: A patient's lab investigations show decreased T3, decreased T4, and decreased TSH. Which of the following conditions is NOT a possible diagnosis?

Primary hypothyroidism. ### Explanation The key to solving this question lies in understanding the **Hypothalamic-Pituitary-Thyroid (HPT) axis** and the concept of negative feedback [1]. **1. Why Primary Hypothyroidism is the Correct Answer:** In **Primary Hypothyroidism**, the pathology lies within the thyroid gland itself (e.g., Hashimoto's thyroiditis). Because the gland cannot produce enough hormones, **T3 and T4 levels are low**. This lack of hormone removes the negative feedback on the pituitary gland, causing it to compensate by secreting **high levels of TSH** [1], [2]. Therefore, a lab profile of low T3/T4 with *decreased* TSH is physiologically inconsistent with primary hypothyroidism [3]. **2. Analysis of Other Options:** * **Panhypopituitarism (Secondary Hypothyroidism):** This is a classic cause of the "all-low" profile. If the anterior pituitary is diseased, it fails to secrete TSH [2]. Without TSH stimulation, the thyroid gland does not produce T3 and T4 [3]. * **Liver Disease (Euthyroid Sick Syndrome):** In systemic illnesses like liver cirrhosis, there is decreased peripheral conversion of T4 to T3 and alterations in thyroid-binding globulins. In severe or chronic cases, a "low T3, low T4, low/normal TSH" pattern can be seen, often referred to as Non-Thyroidal Illness Syndrome (NTIS). **Clinical Pearls for NEET-PG:** * **Most sensitive initial test** for thyroid dysfunction: **Serum TSH**. * **Primary Hypothyroidism:** ↑ TSH, ↓ T4 [3]. * **Secondary (Central) Hypothyroidism:** ↓/Normal TSH, ↓ T4 [3]. * **Subclinical Hypothyroidism:** ↑ TSH, Normal T4 (Patient is usually asymptomatic) [3]. * **Euthyroid Sick Syndrome:** Characterized initially by isolated **low T3** (due to inhibited 5'-deiodinase activity) with normal TSH. In severe cases, all parameters may drop.

Q: Which of the following findings would help to differentiate between SIADH and psychogenic polydipsia?

Urine osmolality 500 mOsm/L. In both **SIADH** and **Psychogenic Polydipsia**, patients present with **hypotonic hyponatremia** (low serum sodium and low serum osmolality). [2] The key to differentiating them lies in the body's physiological response to water excess, specifically the suppression of Antidiuretic Hormone (ADH). ### Why Option D is Correct * **Psychogenic Polydipsia:** Excessive water intake suppresses ADH. In the absence of ADH, the kidneys maximally dilute the urine to excrete the excess water. [1] Therefore, urine osmolality is typically **very low ( 100 mOsm/L, often >300-500 mOsm/L)**. * A urine osmolality of **500 mOsm/L** is concentrated, which is consistent with SIADH and rules out psychogenic polydipsia. ### Why Other Options are Incorrect * **A & B (BUN and Serum Osmolality):** Both conditions are characterized by **euvolemic hyponatremia**. [2] Dilutional effects lead to low serum osmolality and often low-to-normal BUN in both cases. They do not help in differentiation. * **C (Serum Potassium):** Potassium levels are typically normal in both SIADH and psychogenic polydipsia. Abnormal potassium would point toward other causes like diuretics or adrenal insufficiency. ### NEET-PG High-Yield Pearls * **Diagnostic Criteria for SIADH:** Hyponatremia, low serum osmolality ( 100), and high urine sodium (>40 mEq/L) in a euvolemic patient. * **Uric Acid:** Low serum uric acid (<4 mg/dL) is a classic finding in SIADH due to increased urate excretion. * **Treatment:** Fluid restriction is the first-line treatment for both; however, Vaptans (ADH antagonists) are specific for SIADH.

Q: Addison's disease is caused by?

All of the above. **Explanation:** Addison’s disease (Primary Adrenal Insufficiency) results from the bilateral destruction of the adrenal cortex [2], leading to a deficiency in cortisol, aldosterone, and androgens. For clinical symptoms to manifest, typically >90% of the adrenal cortex must be destroyed. **Why "All of the above" is correct:** * **Tuberculosis (TB):** Historically the most common cause worldwide and still a leading cause in developing nations like India [2]. It typically causes adrenal calcification, visible on imaging [1]. * **HIV/AIDS:** HIV can cause adrenal insufficiency through multiple mechanisms, including opportunistic infections; an HIV test should be performed if risk factors are present [1]. * **Metastatic Carcinomas:** The adrenal glands are highly vascular, making them a common site for metastases. While bilateral involvement is common, clinical Addison’s only occurs if the destruction is near-total, though adrenal metastases are a rare cause of insufficiency compared to other factors [1]. **Clinical Pearls for NEET-PG:** 1. **Autoimmune Adrenalitis:** Currently the **most common cause** of Addison’s disease in developed countries (associated with adrenal autoantibodies) [1]. 2. **Waterhouse-Friderichsen Syndrome:** Acute adrenal destruction due to hemorrhagic infarction, most commonly associated with *Neisseria meningitidis* sepsis. 3. **Diagnosis:** The gold standard screening test is the **ACTH Stimulation Test** (Cosyntropin test) [3]. A subnormal rise in cortisol confirms the diagnosis. 4. **Hyperpigmentation:** A hallmark sign of primary (but not secondary) adrenal insufficiency due to increased ACTH and its precursor POMC, which stimulates melanocytes [1].

Q: What is the criterion for diagnosing diabetes mellitus based on fasting blood glucose levels?

Greater than 126 mg/dL. The diagnosis of Diabetes Mellitus (DM) is standardized globally based on criteria established by the American Diabetes Association (ADA) and WHO [1]. **Explanation of the Correct Answer:** **Option D (Greater than or equal to 126 mg/dL)** is the correct diagnostic threshold for Fasting Plasma Glucose (FPG) [1]. "Fasting" is defined as no caloric intake for at least 8 hours. This specific cutoff is chosen because the risk of microvascular complications, particularly diabetic retinopathy, increases significantly once fasting glucose levels exceed this limit [1]. To confirm a diagnosis in an asymptomatic patient, the test should be repeated on a subsequent day [1]. **Analysis of Incorrect Options:** * **Option A (110 mg/dL):** This was previously used in older WHO criteria for Impaired Fasting Glucose (IFG) but is not the diagnostic threshold for diabetes. * **Option B (116 mg/dL):** This value has no specific clinical significance in current diagnostic guidelines. * **Option C (100 mg/dL):** This is the upper limit of "Normal." A fasting glucose between **100–125 mg/dL** is categorized as **Impaired Fasting Glucose (IFG)**, a state of pre-diabetes [1]. **High-Yield Clinical Pearls for NEET-PG:** * **HbA1c Criteria:** $\geq$ 6.5% is diagnostic of DM; 5.7–6.4% is pre-diabetes. * **OGTT (2-hr post-load):** $\geq$ 200 mg/dL is diagnostic; 140–199 mg/dL is Impaired Glucose Tolerance (IGT). * **Random Blood Glucose:** $\geq$ 200 mg/dL **plus** classic symptoms (polyuria, polydipsia, weight loss) is diagnostic without needing a repeat test [1]. * **Gold Standard for Diagnosis:** While HbA1c is convenient, the **75g Oral Glucose Tolerance Test (OGTT)** remains the most sensitive test.

Q: Anti-thyroglobulin antibodies are seen in which of the following conditions?

Hashimoto thyroiditis. **Explanation:** **Hashimoto Thyroiditis (Correct Answer):** Hashimoto thyroiditis (chronic lymphocytic thyroiditis) is an autoimmune disorder characterized by the destruction of thyroid follicles by cellular and humoral immunity. **Anti-thyroglobulin (Anti-Tg)** antibodies are present in approximately 60-80% of patients, while **Anti-thyroid peroxidase (Anti-TPO)** antibodies are even more sensitive, appearing in over 95% of cases. These antibodies serve as markers of thyroid autoimmunity and are central to the diagnosis. **Analysis of Incorrect Options:** * **Graves Disease:** While Anti-Tg and Anti-TPO can be present in Graves disease, the hallmark and pathognomonic antibody is the **TSH Receptor Antibody (TRAb/TSI)**, which stimulates the gland to cause hyperthyroidism [1]. * **De Quervain Thyroiditis (Subacute Granulomatous):** This is a post-viral inflammatory condition, not an autoimmune one. It is characterized by a high ESR and painful thyroid; thyroid antibodies are typically absent or only transiently/weakly positive due to follicle leakage [2]. * **Subacute Lymphocytic Thyroiditis (Painless Thyroiditis):** Although this is an autoimmune variant (often postpartum), the question asks for the primary association. Hashimoto is the classic and most frequent association for high-titer Anti-Tg antibodies in medical examinations. **High-Yield Clinical Pearls for NEET-PG:** * **Most Sensitive Marker:** Anti-TPO is the most sensitive antibody for Hashimoto thyroiditis. * **Anti-Tg Significance:** Anti-Tg must be measured alongside Serum Thyroglobulin when monitoring **Thyroid Cancer** patients, as the presence of these antibodies can falsely interfere with thyroglobulin assays. * **Histology:** Look for **Hurthle cells** (Askanazy cells) and lymphoid follicles with germinal centers on FNAC/Biopsy in Hashimoto patients. * **Risk:** Hashimoto thyroiditis increases the risk of **B-cell Non-Hodgkin Lymphoma** of the thyroid.

Q: What is the most common cause of hypoparathyroidism?

Surgical removal. The most common cause of hypoparathyroidism (responsible for approximately 75% of cases) is **iatrogenic injury or accidental removal** during neck surgery. This typically occurs during total thyroidectomy, parathyroidectomy, or radical neck dissection for malignancy. The mechanism involves either the inadvertent removal of the glands or, more commonly, the disruption of their delicate blood supply (primarily from the inferior thyroid artery). **2. Why Other Options are Incorrect:** * **Idiopathic:** This is a rare cause, often associated with autoimmune destruction of the parathyroid glands. It can occur in isolation or as part of **Autoimmune Polyglandular Syndrome Type 1 (APS-1)**. * **Familial:** Genetic causes, such as mutations in the *GCM2* gene or DiGeorge Syndrome (22q11.2 deletion), are significant in pediatric populations but are far less common than surgical causes in the general population. * **Postradiation:** While external beam radiation to the neck or radioactive iodine therapy for hyperthyroidism can theoretically damage the glands, it is an extremely rare clinical cause of permanent hypoparathyroidism. **3. High-Yield Clinical Pearls for NEET-PG:** * **Hungry Bone Syndrome:** A state of profound hypocalcemia following parathyroidectomy for hyperparathyroidism, caused by rapid bone remineralization. * **Clinical Signs:** Look for **Chvostek sign** (facial twitching on tapping the facial nerve) and **Trousseau sign** (carpal spasm on inflating a BP cuff). * **ECG Finding:** The classic finding in hypocalcemia/hypoparathyroidism is **QT interval prolongation** [1]. * **Biochemical Profile:** Low Calcium, High Phosphate, and Low PTH [1].

Q: What is the most common malignancy of the endocrine system?

Thyroid cancer. **Explanation:** **Thyroid cancer** is the most common malignancy of the endocrine system, accounting for approximately 90% of all endocrine cancers. Among thyroid malignancies, **Papillary Thyroid Carcinoma (PTC)** is the most frequent subtype (80-85%). The incidence of thyroid cancer has been rising globally, primarily due to increased detection of small papillary microcarcinomas via high-resolution ultrasound. **Analysis of Incorrect Options:** * **Pancreatic cancer:** While the pancreas has endocrine functions (Islets of Langerhans), the vast majority (>95%) of pancreatic cancers are **exocrine** (adenocarcinomas). Endocrine tumors of the pancreas (PanNETs) are relatively rare. * **Pituitary adenoma:** These are common, but they are almost always **benign**. True pituitary carcinomas (malignancies with systemic metastasis) are exceedingly rare, representing less than 0.2% of pituitary tumors. * **Adrenal malignancy:** Adrenocortical carcinoma (ACC) is a rare and aggressive tumor with an incidence of only 1-2 per million population per year, making it far less common than thyroid cancer. **High-Yield Clinical Pearls for NEET-PG:** * **Most common thyroid cancer:** Papillary Carcinoma (associated with *BRAF* mutations and Psammoma bodies). * **Most common thyroid cancer post-radiation:** Papillary Carcinoma. * **Medullary Thyroid Carcinoma (MTC):** Arises from parafollicular C-cells; secretes Calcitonin; associated with **MEN 2A and 2B**. * **Anaplastic Carcinoma:** The most aggressive thyroid malignancy with the worst prognosis. * **Orphan Annie Eye nuclei:** Pathognomonic histological feature of Papillary Thyroid Carcinoma.

Q: Wolfram disease includes all of the following except?

Optic glioma. **Explanation:** Wolfram syndrome is a rare, autosomal recessive neurodegenerative disorder caused by mutations in the **WFS1 gene** (encoding the protein Wolframin). It is classically defined by the mnemonic **DIDMOAD**, which represents its four core clinical features. **Why Optic Glioma is the correct answer:** Optic glioma is a benign tumor of the optic nerve most commonly associated with **Neurofibromatosis Type 1 (NF1)**, not Wolfram syndrome. While Wolfram syndrome involves the optic nerve, it presents as **Optic Atrophy** (progressive loss of vision), not a neoplastic growth like a glioma. **Analysis of incorrect options (Features of DIDMOAD):** * **Diabetes Insipidus (A):** Specifically Central Diabetes Insipidus, occurring in about 70% of patients due to vasopressin deficiency. * **Diabetes Mellitus (C):** Typically the first manifestation (usually diagnosed around age 6). It is non-autoimmune (insulin-dependent but antibody-negative). * **Neural Deafness (D):** Sensorineural hearing loss, often affecting high frequencies, typically developing in the second decade of life. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** Autosomal Recessive (WFS1 gene on Chromosome 4p). * **Mnemonic (DIDMOAD):** **D**iabetes **I**nsipidus, **D**iabetes **M**ellitus, **O**ptic **A**trophy, and **D**eafness. * **Additional Features:** Urinary tract abnormalities (dilated renal pelvis, neurogenic bladder) and neurological/psychiatric symptoms (ataxia, depression). * **Prognosis:** It is a progressive disease; the median age of death is usually in the 30s, often due to central apnea or renal failure.

Q: Symptoms of hyperthyroidism include which of the following?

Palpitations. **Explanation:** Hyperthyroidism is a clinical state resulting from excessive circulating thyroid hormones ($T_3$ and $T_4$), which leads to a hypermetabolic state and increased sensitivity to catecholamines. **Why Palpitations is Correct:** Thyroid hormones have a direct stimulatory effect on the myocardium and upregulate $\beta$-adrenergic receptors. This increases heart rate (tachycardia) and myocardial contractility. Patients frequently experience **palpitations**, and in elderly patients or severe cases, this can progress to atrial fibrillation or high-output heart failure [1]. **Analysis of Incorrect Options:** * **A. Intolerance to cold:** This is a classic symptom of **hypothyroidism**. In hyperthyroidism, increased basal metabolic rate (BMR) leads to excessive heat production, resulting in **heat intolerance** and increased sweating [2]. * **B. Decreased appetite:** Hyperthyroidism typically causes an **increased appetite (polyphagia)** due to the high metabolic demand [2]. A decreased appetite is more characteristic of hypothyroidism or systemic illness. * **C. Weight gain:** Despite increased food intake, patients with hyperthyroidism usually experience **weight loss** because the metabolic rate exceeds caloric intake [2]. Weight gain is a hallmark of hypothyroidism. **NEET-PG High-Yield Pearls:** * **Most common cause:** Graves' Disease (associated with exophthalmos and pretibial myxedema) [2]. * **Cardiovascular signs:** Sinus tachycardia is the most common sign; Atrial Fibrillation occurs in 10-15% of patients [1]. * **Neuromuscular:** Look for fine tremors of outstretched hands and proximal muscle weakness (thyrotoxic myopathy) [2]. * **Apathetic Hyperthyroidism:** In elderly patients, typical hypermetabolic features may be absent; they may present only with depression, weight loss, or atrial fibrillation.

Question 1

A patient's lab investigations show decreased T3, decreased T4, and decreased TSH. Which of the following conditions is NOT a possible diagnosis?

Accepted Answer

Primary hypothyroidism

Answer

Panhypopituitarism

Answer

Liver disease

Answer

None of the above

Question 2

Which of the following findings would help to differentiate between SIADH and psychogenic polydipsia?

Accepted Answer

Urine osmolality 500 mOsm/L

Answer

Blood urea nitrogen (BUN) 16 mg/dL

Answer

Serum osmolality 265 mOsm/L

Answer

Serum potassium 4 meq/L

Question 3

Addison's disease is caused by?

Accepted Answer

All of the above

Answer

Tuberculosis

Answer

HIV

Answer

Metastatic carcinomas

Question 4

What is the criterion for diagnosing diabetes mellitus based on fasting blood glucose levels?

Accepted Answer

Greater than 126 mg/dL

Answer

Greater than 110 mg/dL

Answer

Greater than 116 mg/dL

Answer

Greater than 100 mg/dL

Question 5

Anti-thyroglobulin antibodies are seen in which of the following conditions?

Accepted Answer

Hashimoto thyroiditis

Answer

Graves disease

Answer

De Quervain thyroiditis

Answer

Subacute lymphocytic thyroiditis

Question 6

What is the most common cause of hypoparathyroidism?

Accepted Answer

Surgical removal

Answer

Idiopathic

Answer

Familial

Answer

Postradiation

Question 7

What is the most common malignancy of the endocrine system?

Accepted Answer

Thyroid cancer

Answer

Pancreatic cancer

Answer

Pituitary adenoma

Answer

Adrenal malignancy

Question 8

Wolfram disease includes all of the following except?

Accepted Answer

Optic glioma

Answer

Diabetes insipidus

Answer

Diabetes mellitus

Answer

Neural deafness

Question 9

Symptoms of hyperthyroidism include which of the following?

Accepted Answer

Palpitations

Answer

Intolerance to cold

Answer

Decreased appetite

Answer

Weight gain

Question 10

Which of the following is NOT a life-threatening complication of diabetes mellitus?

Accepted Answer

Emphysematous appendicitis

Answer

Malignant otitis externa

Answer

Rhinocerebral mucormycosis

Answer

Emphysematous pyelonephritis

Endocrinology — MCQs

Endocrinology — MCQs

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