Endocrinology Practice Questions

Q: A 27-year-old man and his 24-year-old wife have been trying to conceive a child for 6 years. Physical examination shows he has bilateral gynecomastia, reduced testicular size, reduced body hair, and increased length between the soles of his feet and the pubic bone. A semen analysis indicates oligospermia. Laboratory studies show increased follicle-stimulating hormone level and slightly decreased testosterone level. Which of the following karyotypes is this man most likely to have?

47, XXY. The clinical presentation of infertility, bilateral gynecomastia, small testes, and eunuchoid body habitus (increased sole-to-pubis length) is classic for **Klinefelter Syndrome (47, XXY)** [1]. **Why 47, XXY is correct:** Klinefelter syndrome is the most common cause of primary hypogonadism in males. The extra X chromosome leads to **dysgenesis of seminiferous tubules** (causing low inhibin and high FSH) and **atrophy of Leydig cells** (causing low testosterone and high LH) [1]. The high LH/FSH ratio and peripheral conversion of androgens to estrogens result in gynecomastia [3]. The "eunuchoid" habitus occurs because testosterone is required to close the epiphyseal plates; its deficiency leads to delayed closure and disproportionately long limbs [1]. **Analysis of Incorrect Options:** * **46, X, i(Xq):** This represents an isochromosome X, a variant of **Turner Syndrome** [2]. This would present in a phenotypic female with short stature and primary amenorrhea. * **47, XYY:** Known as **Jacob’s Syndrome**. These individuals are usually phenotypically normal, very tall, and may have severe acne or behavioral issues, but they typically have normal fertility and testosterone levels. * **46, XX/47, XX, +21:** This is a mosaic form of **Down Syndrome**. While it can cause hypogonadism, it is characterized by distinct facies, intellectual disability, and Simian creases, which are absent here. **High-Yield Clinical Pearls for NEET-PG:** * **Most common genotype:** 47, XXY (due to maternal meiotic non-disjunction). * **Key Lab Findings:** ↑ FSH, ↑ LH, ↓ Testosterone, ↑ Estrogen [1]. * **Histology:** Hyalinization and fibrosis of seminiferous tubules [1]. * **Increased Risks:** Breast cancer (20x higher than normal males), extragonadal germ cell tumors, and autoimmune diseases (SLE) [3]. * **Semen Analysis:** Usually shows **azoospermia** (complete absence) or severe oligospermia [1].

Q: Food-dependent Cushing's syndrome is a result of the aberrant expression of which of the following?

Gastric inhibitory polypeptide. **Explanation:** **Food-dependent Cushing’s syndrome** is a rare form of ACTH-independent macronodular adrenal hyperplasia (AIMAH). The underlying pathophysiology involves the **aberrant expression of receptors for Gastric Inhibitory Polypeptide (GIP)** on the adrenal cortex [1]. 1. **Why GIP is correct:** Normally, GIP is a hormone secreted by the K-cells of the small intestine in response to food intake. In this pathological state, the adrenal glands ectopically express GIP receptors. Consequently, every time the patient eats, the postprandial rise in GIP stimulates the adrenal glands to secrete cortisol, leading to hypercortisolism that is specifically triggered by meals [1]. 2. **Why other options are incorrect:** * **Somatostatin:** Generally acts as an inhibitory hormone in the endocrine system; its receptors are often targets for treatment (e.g., octreotide), not the cause of food-dependent Cushing’s. * **Substance P and Tachykinins:** These are neuropeptides involved in pain transmission and smooth muscle contraction; they do not have a recognized role in the postprandial regulation of adrenal cortisol secretion. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** Characterized by low morning (fasting) cortisol levels and high postprandial cortisol levels. * **ACTH Levels:** ACTH will be suppressed (ACTH-independent) because the cortisol excess is driven by GIP, not the pituitary [1]. * **Other Ectopic Receptors:** Besides GIP, AIMAH can also be caused by aberrant expression of receptors for **Beta-adrenergic agonists**, **Vasopressin (V1)**, or **LH/hCG** [1]. * **Treatment:** Often involves bilateral adrenalectomy or, in some GIP-dependent cases, octreotide to suppress GIP release.

Q: Type I diabetes mellitus is associated with which of the following?

Islet cell autoantibodies. ### Explanation **Correct Answer: C. Islet cell autoantibodies** **Medical Concept:** Type 1 Diabetes Mellitus (T1DM) is primarily an **autoimmune disease** characterized by the T-cell-mediated destruction of pancreatic beta cells [1]. The presence of **islet cell autoantibodies** (e.g., GAD65, IA-2, Zinc transporter 8, and Insulin autoantibodies) serves as a hallmark marker of this autoimmune process [2]. These antibodies are often present years before clinical symptoms appear and are used to differentiate T1DM from Type 2 DM or Monogenic diabetes. **Analysis of Incorrect Options:** * **A. Insulin resistance:** This is the primary pathophysiological feature of **Type 2 Diabetes Mellitus (T2DM)** and metabolic syndrome. In T1DM, the problem is an absolute deficiency of insulin, not resistance to its action. * **B. Defect in mitochondrial DNA:** This is associated with **Maternally Inherited Diabetes and Deafness (MIDD)**. It follows a non-Mendelian inheritance pattern and is not the mechanism for classic T1DM. * **C. Beta cell dysfunction:** While beta cells are destroyed in T1DM, "dysfunction" (impaired secretion despite cells being present) is more characteristic of the early stages of **T2DM** or **MODY** [3]. In T1DM, there is beta-cell **destruction** leading to absolute deficiency. **High-Yield Clinical Pearls for NEET-PG:** * **HLA Association:** T1DM is strongly linked to **HLA-DR3 and HLA-DR4** [2]. * **Most Common Antibody:** **GAD65 (Glutamic Acid Decarboxylase)** antibodies are the most persistent and commonly tested. * **Honey Moon Phase:** A transient period after diagnosis where the remaining beta cells function temporarily before total exhaustion. * **Histology:** The classic finding in T1DM is **Insulitis** (lymphocytic infiltration of the islets).

Q: On thyroid function tests, the TSH value is raised and the T4 value is decreased. What is the referred diagnosis?

Primary hypothyroidism. The diagnosis of thyroid disorders relies on the feedback loop between the anterior pituitary (TSH) and the thyroid gland (T4/T3) [1]. **1. Why Primary Hypothyroidism is correct:** In **Primary Hypothyroidism**, the pathology lies within the thyroid gland itself (e.g., Hashimoto’s thyroiditis) [1], [2]. The gland fails to produce sufficient Thyroxine (T4). Due to the loss of negative feedback, the pituitary gland compensates by increasing the secretion of **Thyroid Stimulating Hormone (TSH)**. Therefore, the classic biochemical profile is a **High TSH and Low T4** [1]. **2. Analysis of Incorrect Options:** * **Hyperthyroidism:** Characterized by an overactive gland, resulting in **High T4** and a suppressed (**Low**) **TSH** [1]. * **Secondary Hypothyroidism:** The pathology is in the pituitary or hypothalamus. Since the pituitary cannot produce TSH, both **TSH and T4 are Low** [2]. * **Subclinical Hypothyroidism:** This is an early stage of thyroid failure where the **TSH is High**, but the thyroid gland still manages to maintain a **Normal T4** level. The patient is often asymptomatic. **Clinical Pearls for NEET-PG:** * **Best Screening Test:** Serum TSH is the most sensitive initial test for thyroid dysfunction. * **Hashimoto’s Thyroiditis:** The most common cause of primary hypothyroidism in iodine-sufficient regions; associated with **Anti-TPO antibodies**. * **Wolff-Chaikoff Effect:** Hypothyroidism induced by excessive iodine ingestion. * **Myxedema Coma:** The most severe expression of hypothyroidism, characterized by altered mental status and hypothermia.

Q: Which of the following drugs is NOT used for the treatment of osteoporosis?

Steroids. The correct answer is **Steroids**. In fact, steroids (Glucocorticoids) are a primary **cause** of secondary osteoporosis rather than a treatment for it [1]. **1. Why Steroids are the correct answer:** Glucocorticoids induce bone loss through multiple mechanisms: they inhibit osteoblast (bone-forming cell) activity, increase osteoclast (bone-resorbing cell) lifespan, and decrease intestinal calcium absorption. Chronic steroid use (≥5 mg/day of prednisolone for >3 months) is the most common cause of drug-induced osteoporosis [1]. **2. Why the other options are incorrect:** * **Bisphosphonates (e.g., Alendronate, Zoledronic acid):** These are the **first-line** treatment for osteoporosis. They work by inhibiting osteoclast-mediated bone resorption [1]. * **Denosumab:** This is a monoclonal antibody against **RANKL**. By inhibiting RANKL, it prevents the maturation of osteoclasts, thereby increasing bone mineral density (BMD) [1]. * **Calcium:** Adequate calcium intake (along with Vitamin D) is the foundational requirement for preventing and managing osteoporosis, ensuring the mineralization of the bone matrix [1]. **Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** Dual-energy X-ray absorptiometry (DEXA) scan; Osteoporosis is defined as a **T-score ≤ -2.5**. * **Teriparatide:** A recombinant PTH analogue; it is the only **anabolic** agent (builds bone) commonly used, unlike bisphosphonates which are anti-resorptive. * **Drug of choice for postmenopausal osteoporosis:** Bisphosphonates. * **Side effect of Bisphosphonates:** Osteonecrosis of the jaw (ONJ) and atypical femoral fractures (with long-term use) [1].

Q: A 32-year-old male with suspected neurofibromatosis presented with a blood pressure of 178/110 mm Hg, palpitations, and excessive sweating. Today, his blood pressure is 130/80 mm Hg. Physical examination reveals multiple tumors of the oral mucosa and skin. Laboratory investigations reveal: Serum K+: 3.8 mEq/L, Serum Ca2+: 9.4 mg/dL. Genetic studies in this patient will most likely show which of the following?

RET oncogene. The patient presents with the classic triad of **Pheochromocytoma** (paroxysmal hypertension, palpitations, and diaphoresis) and physical findings of **mucosal neuromas** (oral tumors). This clinical constellation is pathognomonic for **Multiple Endocrine Neoplasia Type 2B (MEN 2B)**. **1. Why RET oncogene is correct:** MEN 2B is characterized by Medullary Thyroid Carcinoma (MTC), Pheochromocytoma, mucosal neuromas, and a Marfanoid habitus. Unlike MEN 2A, it does not typically involve primary hyperparathyroidism (explaining the normal Serum Ca²⁺). Both MEN 2A and MEN 2B are caused by germline mutations in the **RET proto-oncogene** (a receptor tyrosine kinase). In MEN 2B, the mutation is most commonly at codon 918. **2. Why other options are incorrect:** * **N-myc amplification:** Associated with **Neuroblastoma**, the most common extracranial solid tumor in children, not MEN syndromes. * **Overexpression of C-kit:** Associated with **Gastrointestinal Stromal Tumors (GIST)** and systemic mastocytosis. * **K-ras mutation:** Commonly found in **pancreatic, colorectal, and lung adenocarcinomas**, but not linked to the MEN spectrum. **Clinical Pearls for NEET-PG:** * **MEN 2A:** MTC + Pheochromocytoma + Parathyroid Hyperplasia (RET mutation). * **MEN 2B:** MTC + Pheochromocytoma + Mucosal Neuromas/Marfanoid habitus (RET mutation). * **Rule of 10s for Pheochromocytoma:** 10% bilateral, 10% malignant, 10% extra-adrenal, 10% familial. * **Diagnosis:** Best initial test for Pheochromocytoma is plasma free metanephrines; confirmatory test is 24-hour urinary catecholamines/metanephrines.

Question 1

A 27-year-old man and his 24-year-old wife have been trying to conceive a child for 6 years. Physical examination shows he has bilateral gynecomastia, reduced testicular size, reduced body hair, and increased length between the soles of his feet and the pubic bone. A semen analysis indicates oligospermia. Laboratory studies show increased follicle-stimulating hormone level and slightly decreased testosterone level. Which of the following karyotypes is this man most likely to have?

Accepted Answer

47, XXY

Answer

46, X, i(Xq)

Answer

47, XYY

Answer

46, XX/47, XX, +21

Question 2

Food-dependent Cushing's syndrome is a result of the aberrant expression of which of the following?

Accepted Answer

Gastric inhibitory polypeptide

Answer

Somatostatin

Answer

Substance P

Answer

Tachykinins

Question 3

A 54-year-old man presents with 7 weeks of facial flushing and diarrhea. His symptoms began intermittently but are becoming more constant. A 24-hour urine collection reveals an elevated level of 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of serotonin. An abdominal CT scan shows a 2-cm mesenteric mass in the ileum and likely metastatic tumors in the liver. What is the likely diagnosis?

Accepted Answer

Malignant carcinoid syndrome

Answer

Serotonin syndrome

Answer

Cushing syndrome

Answer

Phaeochromocytoma

Question 4

Type I diabetes mellitus is associated with which of the following?

Accepted Answer

Islet cell autoantibodies

Answer

Insulin resistance

Answer

Defect in mitochondrial DNA

Answer

Beta cell dysfunction

Question 5

A male patient presents with headache, profuse sweating, palpitations, and a blood pressure of 160/110 mmHg. Which drug would be most useful in this situation?

Accepted Answer

Phenoxybenzamine

Answer

Nifedipine

Answer

Labetalol

Answer

Prazosin

Question 6

On thyroid function tests, the TSH value is raised and the T4 value is decreased. What is the referred diagnosis?

Accepted Answer

Primary hypothyroidism

Answer

Hyperthyroidism

Answer

Secondary hypothyroidism

Answer

Subclinical hypothyroidism

Question 7

A 35-year-old mother of two children presents with amenorrhea for the last 12 months. She has a history of failure of lactation following her second delivery but remained asymptomatic thereafter. Skull X-ray shows an empty sella. What is the diagnosis?

Accepted Answer

Sheehan's syndrome

Answer

Menopause

Answer

Pituitary tumor

Answer

Intraductal papilloma of the breast

Question 8

Which of the following drugs is NOT used for the treatment of osteoporosis?

Accepted Answer

Steroids

Answer

Bisphosphonates

Answer

Denosumab

Answer

Calcium

Question 9

A 32-year-old male with suspected neurofibromatosis presented with a blood pressure of 178/110 mm Hg, palpitations, and excessive sweating. Today, his blood pressure is 130/80 mm Hg. Physical examination reveals multiple tumors of the oral mucosa and skin. Laboratory investigations reveal: Serum K+: 3.8 mEq/L, Serum Ca2+: 9.4 mg/dL. Genetic studies in this patient will most likely show which of the following?

Accepted Answer

RET oncogene

Answer

N-myc amplification

Answer

Overexpression of C-kit

Answer

K-ras mutation

Question 10

A 35-year-old woman complains of attacks of breathlessness, cyanosis, and flushing. Apart from occasional diarrhea, she has no abdominal symptoms. Abdominal examination reveals an enlarged, nodular liver. If laparotomy is performed, what finding would be expected?

Accepted Answer

An appendicular carcinoid

Answer

An ovarian tumor

Answer

A multicentric hepatoma

Answer

Crohn's disease

Endocrinology — MCQs

Endocrinology — MCQs

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