Endocrinology Practice Questions

Q: Thyrotoxic periodic paralysis (TPP) is usually due to hypokalemia. What is the best treatment?

Propranolol. ### Explanation **Correct Answer: D. Propranolol** **Mechanism and Rationale:** Thyrotoxic periodic paralysis (TPP) is characterized by sudden muscle weakness due to an **intracellular shift of potassium**, rather than a true total-body potassium deficit. Excess thyroid hormone increases **Na+/K+-ATPase pump activity**, a process mediated by **beta-adrenergic stimulation**. **Propranolol** (a non-selective beta-blocker) is the treatment of choice because it directly antagonizes the hyper-adrenergic state, reversing the intracellular shift and normalizing serum potassium levels without the risk of rebound hyperkalemia [1]. **Why other options are incorrect:** * **A. Potassium:** While hypokalemia is present, giving intravenous potassium is risky. Since there is no actual loss of potassium from the body, as the attack resolves, the potassium shifts back into the extracellular space. Exogenous administration often leads to **rebound hyperkalemia** (seen in up to 40% of cases). If used, it must be given in very low doses and with extreme caution. * **B. Magnesium:** Magnesium deficiency can coexist with hypokalemia, but it is not the primary pathophysiology of TPP. * **C. Hydration:** While supportive, hydration does not address the underlying ion shift or the thyrotoxic state [1]. **NEET-PG High-Yield Pearls:** * **Demographics:** TPP is most common in **Asian males**, despite hyperthyroidism being more common in females. * **Triggers:** High carbohydrate meals (insulin release) and strenuous exercise followed by rest. * **Definitive Treatment:** Achieving a **euthyroid state** (e.g., antithyroid drugs, radioactive iodine, or surgery) is the only way to prevent recurrence [1]. * **Key Distinction:** Unlike Familial Periodic Paralysis, TPP patients will show signs of hyperthyroidism (tachycardia, tremors, low TSH).

Q: Nelson syndrome is seen following which surgical procedure?

Adrenalectomy. **Explanation:** **Nelson Syndrome** is a clinical condition characterized by the rapid enlargement of a pre-existing ACTH-secreting pituitary adenoma following a **bilateral total adrenalectomy**. **Why Adrenalectomy is the correct answer:** In patients with Cushing’s disease (pituitary-driven hypercortisolism), the high levels of circulating cortisol normally provide negative feedback to the pituitary gland. When a bilateral adrenalectomy is performed to control symptoms, this negative feedback is abruptly removed. In the absence of cortisol, the underlying pituitary microadenoma undergoes aggressive growth and hypersecretion of ACTH. This leads to the classic triad of: 1. **Hyperpigmentation** (due to high ACTH levels stimulating melanocytes). 2. **Mass effect symptoms** (headaches, visual field defects like bitemporal hemianopia). 3. **Very high serum ACTH levels.** **Why other options are incorrect:** * **Cholecystectomy:** Removal of the gallbladder; associated with Post-cholecystectomy syndrome, not endocrine feedback loops. * **Splenectomy:** Removal of the spleen; associated with OPSI (Overwhelming Post-Splenectomy Infection) and Howell-Jolly bodies. * **Duodenectomy:** Part of a Whipple’s procedure; associated with malabsorption or dumping syndrome, but has no direct effect on the pituitary-adrenal axis. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnostic Marker:** Markedly elevated plasma ACTH levels and MRI evidence of an enlarging pituitary mass. * **Prevention:** Prophylactic pituitary irradiation or careful monitoring of ACTH levels post-adrenalectomy. * **Treatment:** Transsphenoidal surgery (TSS) or radiotherapy to the pituitary gland. * **Key Association:** Always remember: **Bilateral Adrenalectomy → Loss of Negative Feedback → Nelson Syndrome.**

Q: Impaired oral glucose tolerance test (OGTT) is indicated by which of the following criteria?

Fasting blood glucose < 126 mg/dL and two hours after glucose load 140-199 mg/dL. The diagnosis of glycemic status is based on specific thresholds defined by the American Diabetes Association (ADA). **Impaired Glucose Tolerance (IGT)** is a state of "Pre-diabetes" where blood glucose levels are higher than normal but do not yet meet the criteria for a diagnosis of Diabetes Mellitus [1]. **1. Why Option D is Correct:** The Oral Glucose Tolerance Test (OGTT) involves administering 75g of anhydrous glucose. IGT is specifically defined as a **2-hour post-load plasma glucose between 140 mg/dL and 199 mg/dL**. To fit the definition of IGT (rather than overt diabetes), the fasting plasma glucose must also be below the diabetic threshold ( 126 mg/dL):** This is the diagnostic threshold for **Diabetes Mellitus**, not impaired tolerance [1]. * **Option B (Random > 200 mg/dL):** A random plasma glucose ≥ 200 mg/dL in a symptomatic patient (polyuria, polydipsia) is diagnostic of **Diabetes Mellitus**. * **Option C (Fasting < 90 mg/dL):** This represents a normal fasting glucose level (Normal is < 100 mg/dL). **3. NEET-PG High-Yield Pearls:** * **Impaired Fasting Glucose (IFG):** Fasting plasma glucose between **100–125 mg/dL**. * **HbA1c Criteria:** Normal (< 5.7%), Pre-diabetes (5.7–6.4%), and Diabetes (≥ 6.5%). * **Gold Standard:** While HbA1c is convenient, the **OGTT** is considered more sensitive for diagnosing early glucose intolerance. * **Pregnancy (GDM):** Note that the Carpenter-Coustan or DIPSI criteria used in pregnancy have different thresholds than the general population.

Q: Syndrome of inappropriate ADH secretion is commonly associated with which of the following malignancies?

Lung carcinoma. Explanation: Syndrome of Inappropriate Antidiuretic Hormone (SIADH) is a common paraneoplastic syndrome characterized by the autonomous, non-physiological secretion of ADH, leading to water retention and dilutional hyponatremia. Why Lung Carcinoma is Correct: Among all malignancies, Small Cell Lung Carcinoma (SCLC) is the most frequent cause of SIADH [1]. Approximately 7–10% of patients with SCLC develop SIADH because the neuroendocrine tumor cells ectopically produce and secrete arginine vasopressin (ADH) [1]. It is a classic high-yield association in clinical medicine. Analysis of Incorrect Options: * Breast and Ovarian Carcinoma: While these can occasionally be associated with paraneoplastic syndromes (like hypercalcemia of malignancy due to PTHrP), they are not classically or commonly associated with SIADH [1]. * Hepatocellular Carcinoma: This is more frequently associated with paraneoplastic erythrocytosis (due to EPO production) or hypoglycemia, but rarely SIADH [1]. NEET-PG High-Yield Pearls: * Most common cause of SIADH overall: Small Cell Lung Cancer (SCLC) [1]. * Diagnosis: Characterized by hyponatremia, low serum osmolality ( 100 mOsm/kg) in a euvolemic patient. * Management: The mainstay of treatment for chronic SIADH is fluid restriction. For symptomatic/severe hyponatremia, hypertonic saline (3%) is used. Vaptans (Vasopressin receptor antagonists) are pharmacological options. * Complication: Rapid correction of hyponatremia can lead to Osmotic Demyelination Syndrome (Central Pontine Myelinolysis). Remember: "Low to High, your Pons will die."

Q: Which type of diabetes is HLA associated?

Type I diabetes. **Explanation:** **Type 1 Diabetes Mellitus (T1DM)** is an autoimmune disorder characterized by the destruction of pancreatic beta cells [1]. Its pathogenesis is strongly linked to the **Major Histocompatibility Complex (MHC)**, specifically the **HLA class II genes** located on chromosome 6p21 [2]. * **Why Option A is correct:** Approximately 90–95% of children with T1DM carry the high-risk haplotypes **HLA-DR3-DQ2** or **HLA-DR4-DQ8**. These HLA molecules are responsible for presenting islet autoantigens to T-lymphocytes, triggering the autoimmune cascade [1]. Heterozygosity for both (DR3/DR4) confers the highest genetic risk. * **Why other options are incorrect:** * **Type 2 Diabetes (B):** This is primarily a metabolic disorder characterized by insulin resistance and relative insulin deficiency. While it has a stronger overall genetic component (higher concordance in identical twins) than T1DM, it is **polygenic** and not associated with HLA or autoimmune markers [1]. * **Malnutrition-related Diabetes (C):** Now largely classified under "Other specific types," this is associated with environmental factors (protein deficiency/cassava toxins) and pancreatic calcification, not HLA-mediated autoimmunity [3]. * **Pregnancy-related Diabetes (D):** Gestational Diabetes (GDM) is driven by placental hormones (like Human Placental Lactogen) causing insulin resistance; it does not have an HLA association. **High-Yield Clinical Pearls for NEET-PG:** 1. **Strongest Association:** HLA-DR3 and HLA-DR4 [1]. 2. **Protective Allele:** HLA-DQB1*0602 is known to provide protection against T1DM. 3. **Autoantibodies:** The presence of GAD65, IA-2, and Zinc Transporter 8 (ZnT8) antibodies confirms the autoimmune nature of T1DM [2]. 4. **LADA:** Latent Autoimmune Diabetes in Adults also shows HLA associations similar to T1DM.

Question 1

Which of the following is the most likely cause of hirsutism, when associated with anovulation, obesity, and amenorrhea?

Accepted Answer

Polycystic ovarian disease (PCOD)

Answer

Drug-induced hirsutism

Answer

Adrenal tumor

Answer

Idiopathic hirsutism

Question 2

Thyrotoxic periodic paralysis (TPP) is usually due to hypokalemia. What is the best treatment?

Accepted Answer

Propranolol

Answer

Potassium

Answer

Magnesium

Answer

Hydration

Question 3

Nelson syndrome is seen following which surgical procedure?

Accepted Answer

Adrenalectomy

Answer

Cholecystectomy

Answer

Spleenectomy

Answer

Duodenectomy

Question 4

Impaired oral glucose tolerance test (OGTT) is indicated by which of the following criteria?

Accepted Answer

Fasting blood glucose < 126 mg/dL and two hours after glucose load 140-199 mg/dL

Answer

Fasting plasma glucose 
> 126 mg/dL

Answer

Random blood glucose > 200 mg/dL

Answer

Fasting blood glucose < 90 mg/dL

Question 5

What is the most diagnostic test for Addison's disease?

Accepted Answer

ACTH stimulation test

Answer

Serum Na+, K+, and renin levels

Answer

Serum Na+, K+, and saline suppression test

Answer

Serum creatinine/urea ratio

Question 6

A 29-year-old woman complains of nervousness and muscle weakness of 6 months' duration. She is intolerant of heat and sweats excessively. She has lost 9 kg over the past 6 months despite an increased caloric intake. She frequently experiences a racing heart and palpitations. She has also missed several menstrual periods in the past few months. Physical examination reveals warm, moist skin and exophthalmos. What endocrine abnormality is most likely present in this patient?

Accepted Answer

Increased anti-TSH receptor antibodies

Answer

Increased anti-thyroid DNA antibodies

Answer

Decreased uptake of radioactive iodine in the thyroid

Answer

Increased serum TSH

Question 7

Syndrome of inappropriate ADH secretion is commonly associated with which of the following malignancies?

Accepted Answer

Lung carcinoma

Answer

Breast carcinoma

Answer

Ovarian carcinoma

Answer

Hepatocellular carcinoma

Question 8

In a woman with polyuria of 6L/day, which are the 2 most important investigations to be done?

Accepted Answer

Water deprivation test

Answer

Plasma and urine osmolality

Answer

Water loading test

Answer

Plasma osmolality

Question 9

Which type of diabetes is HLA associated?

Accepted Answer

Type I diabetes

Answer

Type II diabetes

Answer

Malnutrition-related diabetes

Answer

Pregnancy-related diabetes

Question 10

Which of the following is the most likely clinical feature associated with high prolactin levels causing sexual dysfunction?

Accepted Answer

Failure of erection with absent nocturnal penile tumescence (NPT)

Answer

Loss of sexual desire

Answer

Absence of emission

Answer

Absence of orgasm with normal libido and erectile function

Endocrinology — MCQs

Endocrinology — MCQs

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