Endocrinology Practice Questions

Q: What is the primary hormone secreted by an extra-adrenal pheochromocytoma?

Norepinephrine. **Explanation:** The correct answer is **Norepinephrine**. **1. Why Norepinephrine is correct:** Extra-adrenal pheochromocytomas (also known as **paragangliomas**) arise from the sympathetic chain or the Organ of Zuckerkandl [1]. Unlike the adrenal medulla, extra-adrenal chromaffin tissue lacks the enzyme **Phenylethanolamine N-methyltransferase (PNMT)**. This enzyme is responsible for converting norepinephrine into epinephrine and requires high concentrations of cortisol (from the adjacent adrenal cortex) to be induced. Since extra-adrenal sites lack this proximity to cortisol and the PNMT enzyme, they predominantly secrete **norepinephrine** [1]. **2. Why other options are incorrect:** * **Epinephrine:** This is primarily secreted by **intra-adrenal** pheochromocytomas because the adrenal medulla contains the PNMT enzyme [1]. A tumor secreting purely epinephrine is almost always located within the adrenal gland. * **Metanephrine:** This is a metabolite of epinephrine, not the primary hormone secreted. While metanephrines are diagnostic markers measured in urine/plasma, they are breakdown products. * **Dopamine:** While some paragangliomas (especially carotid body tumors) can secrete dopamine, it is not the "primary" hormone for extra-adrenal pheochromocytomas in general. **3. High-Yield Clinical Pearls for NEET-PG:** * **Rule of 10s:** Traditionally, 10% of pheochromocytomas are extra-adrenal, though recent data suggests this may be higher (up to 15-20%). * **Malignancy:** Extra-adrenal tumors have a higher risk of malignancy compared to adrenal tumors. * **Localization:** The most common extra-adrenal site is the **Organ of Zuckerkandl** (near the origin of the inferior mesenteric artery). * **Diagnosis:** Plasma free metanephrines or 24-hour urinary fractionated metanephrines are the initial screening tests of choice.

Q: A 21-year-old male presented with short stature and lack of secondary sexual characteristics. He underwent surgery for a brain tumor 12 years ago and received cranial radiation. Which of the following is true regarding acquired hypopituitarism due to radiation?

Growth hormone is the most common hormonal deficiency.. Radiation-induced hypopituitarism is a common late complication of cranial irradiation for brain tumors. The pituitary gland and hypothalamus are sensitive to radiation, and the damage is typically **dose-dependent, progressive, and permanent.** [1] **1. Why Option C is Correct:** The anterior pituitary hormones follow a predictable sequence of loss after radiation. **Growth Hormone (GH) deficiency** is almost universally the first to manifest, followed by gonadotropins (LH/FSH), then TSH, and finally ACTH. In pediatric or young adult patients, this typically presents as short stature and delayed puberty, as seen in this case. [2] **2. Why the Other Options are Incorrect:** * **Option A:** At a dose of **50 Gy**, the risk is significantly higher than 5%. Approximately **50–90%** of patients receiving this dose will develop some form of hypothalamic-pituitary dysfunction within 5–10 years. * **Option B:** Radiation-induced damage is not immediate. While some changes occur early, the majority of clinical deficiencies manifest **years (typically 2 to 10 years)** after treatment. It requires long-term surveillance. * **Option D:** **Children and young adults** are at the highest risk. Their developing endocrine axes are more sensitive to radiation damage compared to older adults. **Clinical Pearls for NEET-PG:** * **Sequence of loss:** GH > LH/FSH > TSH > ACTH (Mnemonic: **"Go Look For The Adenoma"** – GH, LH, FSH, TSH, ACTH). * **Hyperprolactinemia:** Unlike other hormones which decrease, prolactin levels may **increase** after radiation due to damage to the hypothalamic dopaminergic pathways (loss of tonic inhibition). * **Primary site of damage:** In many cases of cranial radiation, the **hypothalamus** is more sensitive and is the primary site of injury rather than the pituitary gland itself.

Q: Type I diabetes mellitus may be associated with which of the following conditions?

Celiac Disease. **Explanation:** **1. Why Celiac Disease is Correct:** Type 1 Diabetes Mellitus (T1DM) is an organ-specific autoimmune disorder characterized by the destruction of pancreatic beta cells [2]. It is frequently associated with other **autoimmune polyendocrine syndromes (APS)** because these conditions share a common genetic predisposition, specifically linked to **HLA-DR3 and HLA-DR4** genotypes [2]. Celiac disease is an autoimmune enteropathy triggered by gluten; approximately 5–10% of patients with T1DM are found to have biopsy-proven Celiac disease [1]. Screening for Celiac disease (via tissue transglutaminase antibodies) is a standard clinical recommendation for all newly diagnosed T1DM patients. **2. Analysis of Incorrect Options:** * **Obesity:** This is a hallmark risk factor for **Type 2 Diabetes Mellitus**, characterized by insulin resistance. T1DM patients are typically lean or present with weight loss at diagnosis due to an absolute insulin deficiency and catabolism [2]. * **Down’s Syndrome:** While Down’s syndrome is associated with an increased risk of T1DM and hypothyroidism, it is a chromosomal disorder (Trisomy 21), not an autoimmune condition directly "associated" in the context of shared pathophysiology like Celiac disease. * **Precocious Puberty:** There is no established pathophysiological link between T1DM and precocious puberty. In fact, poorly controlled T1DM is more commonly associated with **delayed puberty** and growth retardation (Mauriac Syndrome). **High-Yield Clinical Pearls for NEET-PG:** * **Common Autoimmune Associations with T1DM:** Hashimoto’s thyroiditis (most common), Graves' disease, Celiac disease, Addison’s disease, and Vitiligo [1]. * **HLA Associations:** HLA-DR3/DR4 and DQ8 are strongly linked to T1DM [2]. * **Screening Rule:** Always screen T1DM patients for **Thyroid Peroxidase (TPO) antibodies** and **Celiac disease** regardless of symptoms.

Q: Which of the following is not a characteristic feature of Graves' disease?

Late diastolic murmur. **Explanation:** **Graves’ disease** is an autoimmune condition characterized by hyperthyroidism due to TSH-receptor antibodies [1]. The correct answer is **Late diastolic murmur**, as this is typically associated with mitral stenosis, not hyperthyroidism. **1. Why "Late diastolic murmur" is the correct answer:** Hyperthyroidism induces a hyperdynamic circulatory state. Cardiovascular findings in Graves' disease include tachycardia, palpitations, and a wide pulse pressure [3]. While a **systolic murmur** (flow murmur) is common due to increased cardiac output, a diastolic murmur is not a feature of thyrotoxicosis. Occasionally, a "Means-Lerman scratch" (a systolic sound mimicking a friction rub) may be heard, but never a late diastolic murmur. **2. Analysis of incorrect options:** * **Hyperreflexia:** Excess thyroid hormone increases neuromuscular excitability and shortens the contraction/relaxation time of muscles, leading to "brisk" deep tendon reflexes. * **Chorea:** Though rare, thyrotoxicosis can manifest as movement disorders, including chorea or tremors, due to increased sensitivity of dopamine receptors in the basal ganglia. * **Lid lag sign (Griffith’s sign):** This is a classic sympathetic overactivity sign where the upper eyelid fails to follow the downward movement of the iris [3]. **Clinical Pearls for NEET-PG:** * **Specific to Graves’:** Exophthalmos (proptosis), Pretibial Myxedema (dermopathy), and Thyroid Acropachy (clubbing) are unique to Graves' and not seen in other forms of hyperthyroidism [1]. * **Cardiac complication:** Atrial Fibrillation is the most common arrhythmia in elderly patients with thyrotoxicosis [2]. * **Diagnosis:** Low TSH, High Free T4, and diffuse uptake on Radionuclide scan [3].

Q: Increased serum calcium and decreased serum phosphate may be seen in all of the following conditions, except:

Vitamin D intoxication. **Explanation:** The biochemical hallmark of **Primary Hyperparathyroidism (PHPT)** and related conditions is the combination of hypercalcemia and hypophosphatemia [1][3]. This occurs because Parathyroid Hormone (PTH) increases bone resorption and renal calcium reabsorption while simultaneously inhibiting phosphate reabsorption in the proximal tubule (phosphaturic effect) [1]. **Why Vitamin D Intoxication is the correct answer:** In Vitamin D intoxication, there is an excess of 1,25-(OH)₂D (Calcitriol). Vitamin D acts on the GI tract and kidneys to **increase the absorption of both Calcium and Phosphate** [1]. Therefore, the biochemical profile shows **increased serum calcium and increased serum phosphate** [2]. This distinguishes it from PTH-mediated hypercalcemia. **Analysis of Incorrect Options:** * **Primary Hyperparathyroidism:** High PTH levels lead to high Ca²⁺ and low PO₄³⁻ due to renal phosphate wasting [3]. * **Hypercalcemia of Malignancy:** Often caused by **PTH-related peptide (PTHrP)** [2]. PTHrP mimics PTH by binding to the same receptors, leading to increased calcium and decreased phosphate. * **Familial Benign Hypercalcemia (FHH):** Caused by an inactivating mutation in the Calcium-Sensing Receptor (CaSR) [1]. The body "perceives" low calcium, leading to inappropriately high PTH levels, which results in hypercalcemia and low-to-normal phosphate [2]. **High-Yield Clinical Pearls for NEET-PG:** 1. **Phosphate Rule:** High Ca + Low PO₄ = PTH-mediated (or PTHrP). High Ca + High PO₄ = Vitamin D-mediated or Bone destruction (e.g., Milk-alkali, Sarcoidosis) [2]. 2. **FHH vs. PHPT:** To differentiate, check urinary calcium [2]. FHH has **low** urinary calcium (Urinary Calcium/Creatinine Clearance Ratio <0.01), whereas PHPT has **high** urinary calcium. 3. **PTHrP:** Most common cause of hypercalcemia in hospitalized patients (Squamous cell CA of lung, Renal cell CA) [2].

Q: All of the following are true regarding Grave's disease except?

Anti-TPO antibodies. **Explanation:** The correct answer is **C (Anti-TPO antibodies)**. While Anti-TPO antibodies can be present in Graves' disease (up to 70-80% of cases), they are **not specific** to it and are the hallmark of Hashimoto’s Thyroiditis. The pathognomonic antibody for Graves' disease is **TSH-Receptor Antibody (TRAb)** [1], specifically Thyroid Stimulating Immunoglobulins (TSI), which mimic TSH and cause hyperthyroidism [2]. **Analysis of Options:** * **A. Orbital proptosis:** This is a classic extrathyroidal manifestation of Graves' disease (Graves' Ophthalmopathy) [1]. It is caused by the inflammation and accumulation of glycosaminoglycans in the retro-orbital tissues, leading to forward displacement of the eye [2]. * **B. Presents as primary thyrotoxicosis:** Graves' disease is the most common cause of primary hyperthyroidism [2]. "Primary" indicates the pathology lies within the thyroid gland itself, characterized by elevated T4/T3 and suppressed TSH [1]. * **D. Pretibial myxoedema:** Also known as localized dermopathy, this is a specific feature of Graves' disease [1]. It presents as non-pitting edema and "orange-peel" (peau d'orange) skin, usually over the anterior tibia. **High-Yield Clinical Pearls for NEET-PG:** * **Triad of Graves:** Hyperthyroidism + Diffuse Goiter + Exophthalmos. * **Radioiodine Uptake (RAIU):** Shows **diffuse, increased uptake** (unlike Toxic Multinodular Goiter which shows "patchy" uptake). * **Most Specific Sign:** Graves' Ophthalmopathy (Proptosis). * **Treatment of Choice:** Antithyroid drugs (Methimazole/PTU) for initial management; Radioiodine (I-131) is the most common definitive therapy in adults [3].

Q: A common cause of Cushing syndrome is:

Pituitary adenoma. Cushing syndrome refers to the clinical state resulting from chronic exposure to excessive glucocorticoids. When the cause is a pituitary adenoma secreting excess ACTH, it is specifically termed **Cushing Disease**. [1] **1. Why Pituitary Adenoma is Correct:** Among the endogenous causes of Cushing syndrome, **Cushing Disease (Pituitary ACTH-secreting adenoma)** is the most common, accounting for approximately **70%** of cases. [1] It typically involves a microadenoma (<10 mm) that stimulates the adrenal cortex to produce excess cortisol bilaterally. [4] **2. Why Other Options are Incorrect:** * **A. Cancer producing ectopic ACTH:** While this is a known cause of ACTH-dependent Cushing syndrome (most commonly Small Cell Carcinoma of the Lung), it is less frequent than pituitary adenomas, accounting for only about 10-15% of cases. [1] * **C. Adrenal Tuberculosis:** This is a classic cause of **Addison’s Disease** (Primary Adrenal Insufficiency), not Cushing syndrome. Tuberculosis destroys the adrenal cortex, leading to a deficiency of cortisol and aldosterone, rather than an excess. **High-Yield Clinical Pearls for NEET-PG:** * **Most Common Cause Overall:** Exogenous (Iatrogenic) administration of glucocorticoids. [1], [3] * **Most Common Endogenous Cause:** Cushing Disease (Pituitary Adenoma). * **Screening Tests:** Overnight Dexamethasone Suppression Test (ONDST), 24-hour urinary free cortisol, or Late-night salivary cortisol. [2], [3] * **Differential Diagnosis:** High-dose dexamethasone suppression test (HDDST) and CRH stimulation test typically show suppression/response in Cushing Disease but *not* in ectopic ACTH production. [4] * **Imaging:** MRI Brain (Pituitary) is the investigation of choice for Cushing Disease. [4]

Question 1

Beta-blockers are used in hyperthyroidism:

Accepted Answer

As short-term symptomatic therapy until the effect of carbimazole develops

Answer

As long-term therapy after subtotal thyroidectomy

Answer

In patients not responding to carbimazole

Answer

To potentiate the effect of radioactive iodine

Question 2

Calciphylaxis is more commonly seen in which of the following conditions?

Accepted Answer

Secondary hyperparathyroidism

Answer

Primary hyperparathyroidism

Answer

Tertiary hyperparathyroidism

Answer

Pseudohyperparathyroidism

Question 3

What is the primary hormone secreted by an extra-adrenal pheochromocytoma?

Accepted Answer

Norepinephrine

Answer

Epinephrine

Answer

Metanephrine

Answer

Dopamine

Question 4

A 21-year-old male presented with short stature and lack of secondary sexual characteristics. He underwent surgery for a brain tumor 12 years ago and received cranial radiation. Which of the following is true regarding acquired hypopituitarism due to radiation?

Accepted Answer

Growth hormone is the most common hormonal deficiency.

Answer

At a dose of 50 Gy of radiation, only 5% of patients will manifest hypopituitarism.

Answer

The majority of patients who develop hypopituitarism after cranial radiation do so within a year of treatment.

Answer

Older adults are at the highest risk from radiation-induced hypopituitarism.

Question 5

Type I diabetes mellitus may be associated with which of the following conditions?

Accepted Answer

Celiac Disease

Answer

Obesity

Answer

Down's syndrome

Answer

Precocious puberty

Question 6

Which of the following is not a characteristic feature of Graves' disease?

Accepted Answer

Late diastolic murmur

Answer

Hyperreflexia

Answer

Chorea

Answer

Lid lag sign

Question 7

Increased serum calcium and decreased serum phosphate may be seen in all of the following conditions, except:

Accepted Answer

Vitamin D intoxication

Answer

Primary hyperparathyroidism

Answer

Hypercalcemia of malignancy

Answer

Familial benign hypercalcemia

Question 8

A 30-year-old female presents with palpitations, increased appetite, and significant weight loss. She also reports a large neck swelling and has abnormal thyroid function tests showing elevated T3 and T4 with suppressed TSH. Her TSH receptor antibody test is negative. Ultrasound of the neck reveals multiple nodules, and a Radioactive Iodine Uptake (RAIU) scan shows increased uptake. After achieving a euthyroid state, what is the best definitive step in management?

Accepted Answer

Near-total thyroidectomy

Answer

Continue antithyroid medication

Answer

Sub-total thyroidectomy

Answer

Radioactive iodine therapy

Question 9

All of the following are true regarding Grave's disease except?

Accepted Answer

Anti-TPO antibodies

Answer

Orbital proptosis

Answer

Presents as primary thyrotoxicosis

Answer

Pretibial myxoedema

Question 10

A common cause of Cushing syndrome is:

Accepted Answer

Pituitary adenoma

Answer

Cancer producing ectopic ACTH

Answer

Adrenal tuberculosis

Answer

None of the above

Endocrinology — MCQs

Endocrinology — MCQs

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