Laboratory Diagnosis of Endocrine Diseases — MCQs
TRH stimulation testing is useful in diagnosis of disorders of the following hormones?
In hypoparathyroidism:
A 30-year-old male presents with erectile dysfunction, low testosterone, and elevated prolactin levels. What is the most likely diagnosis?
A patient presents with symptoms of hyperthyroidism. Thyroid function tests would probably reveal:
Adrenal reserve is best tested by means of infusion with
A 45-year-old man with a recent history of bizarre behavior is seen by a psychiatrist. On physical examination, the patient appears moderately obese with mild hypertension, facial acne, and fat accumulation in the supraclavicular fossae. Laboratory studies demonstrate neutrophilic leukocytosis, decreased lymphocytes, and absence of eosinophils, along with mild hypokalemia and mild metabolic alkalosis. The fasting serum glucose is within the reference range, but the OGTT shows glucose concentrations > 200 mg/dL. Laboratory studies also show a free urinary cortisol of 156 mg/24 hours. Which of the following questions would be of most help in establishing a diagnosis?
The following is a histopathological image of thyroid pathology. What is the diagnosis?
False regarding Alzheimer's disease (AD) is:
Which of the following is the most sensitive and specific initial laboratory test to diagnose iron deficiency?
Classical markers for Hodgkin's disease are
Laboratory Diagnosis of Endocrine Diseases Indian Medical PG Practice Questions and MCQs
Question 1: TRH stimulation testing is useful in diagnosis of disorders of the following hormones?
- A. PTH
- B. ACTH
- C. Insulin
- D. Growth hormone (Correct Answer)
Explanation: ***Growth hormone*** - **TRH** (Thyrotropin-Releasing Hormone) normally stimulates the release of **TSH** and **prolactin** from the anterior pituitary, but **does not normally affect growth hormone**. - In certain pathological conditions like **acromegaly**, TRH can **paradoxically stimulate growth hormone release**, where GH levels abnormally increase instead of remaining unchanged. - This **paradoxical GH response to TRH** is used as a diagnostic test in suspected acromegaly patients, helping differentiate it from normal physiology. - Note: The primary uses of TRH stimulation are for assessing **TSH** (thyroid axis disorders) and **prolactin** (hyperprolactinemia), but among the given options, growth hormone is the relevant answer. *PTH* - **PTH** (Parathyroid Hormone) regulation is primarily controlled by **serum calcium levels**, not by TRH. - Disorders of PTH are diagnosed through **calcium, phosphate, and PTH measurements**, not TRH stimulation. *ACTH* - **ACTH** (Adrenocorticotropic Hormone) release is stimulated by **CRH** (Corticotropin-Releasing Hormone), not TRH. - Conditions involving ACTH are typically evaluated using **CRH stimulation tests** or **dexamethasone suppression tests**. *Insulin* - **Insulin** secretion by pancreatic beta cells is primarily regulated by **blood glucose levels**, not by TRH. - Insulin-related disorders are diagnosed through **glucose tolerance tests**, **C-peptide levels**, and **insulin measurements**.
Question 2: In hypoparathyroidism:
- A. Plasma calcium is high and inorganic phosphorous low
- B. Plasma calcium and inorganic phosphorous are low
- C. Plasma calcium is low and inorganic phosphorous high (Correct Answer)
- D. Plasma calcium and inorganic phosphorous are high
Explanation: ***Plasma calcium is low and inorganic phosphorous high*** - **Hypoparathyroidism** is characterized by insufficient parathyroid hormone (PTH) production, leading to decreased bone resorption and reduced renal reabsorption of calcium [1]. This results in **hypocalcemia** (low plasma calcium) [1]. - PTH also promotes renal excretion of phosphate [2]. With insufficient PTH, renal phosphate excretion is impaired, leading to **hyperphosphatemia** (high inorganic phosphorus) [1]. *Plasma calcium is high and inorganic phosphorous low* - This profile is characteristic of **primary hyperparathyroidism**, where excessive PTH causes increased bone resorption and renal calcium reabsorption (high calcium), and increased renal phosphate excretion (low phosphorus). - It directly contradicts the defining features of hypoparathyroidism [1]. *Plasma calcium and inorganic phosphorous are low* - While plasma calcium is low in hypoparathyroidism, plasma inorganic phosphorus is characteristically high, not low [1]. - A combination of low calcium and low phosphorus can be seen in conditions like **vitamin D deficiency** (osteomalacia), but not directly in pure hypoparathyroidism [1]. *Plasma calcium and inorganic phosphorous are high* - This combination of high calcium and high phosphorus is uncommon and not typically seen in either hypoparathyroidism or hyperparathyroidism. - It could potentially indicate conditions like **milk-alkali syndrome** or **vitamin D intoxication**, but not hypoparathyroidism, which is defined by low calcium [1].
Question 3: A 30-year-old male presents with erectile dysfunction, low testosterone, and elevated prolactin levels. What is the most likely diagnosis?
- A. Craniopharyngioma
- B. Testicular failure
- C. Pituitary adenoma (Correct Answer)
- D. Cushing's syndrome
Explanation: Pituitary adenoma - Elevated prolactin levels in a male, coupled with symptoms of hypogonadism (erectile dysfunction, low testosterone), are highly suggestive of a prolactinoma, which is a type of pituitary adenoma [1]. - The prolactinoma suppresses gonadotropin-releasing hormone (GnRH), leading to secondary hypogonadism [1]. Craniopharyngioma - While it is a suprasellar tumor that can affect pituitary function, it typically causes symptoms related to compression of the optic chiasm (visual field defects) [3] and panhypopituitarism, which are not mentioned here. - Hyperprolactinemia is usually due to stalk compression rather than direct prolactin secretion, and other hormone deficiencies are typically more prominent [1]. Cushing's syndrome - Characterized by elevated cortisol levels, leading to symptoms like central obesity, moon facies, and skin changes, which are not described in this patient [4]. - Although it can sometimes be caused by a pituitary tumor (Cushing's disease), the primary hormonal imbalance is cortisol excess, not isolated hyperprolactinemia. Testicular failure - While it causes low testosterone and erectile dysfunction, it would lead to elevated LH and FSH (hypergonadotropic hypogonadism) due to the lack of negative feedback on the pituitary [2]. - Elevated prolactin is not a direct consequence of primary testicular failure.
Question 4: A patient presents with symptoms of hyperthyroidism. Thyroid function tests would probably reveal:
- A. Increased T4, Increased T3, decreased TSH (Correct Answer)
- B. Increased T4, normal T3, and increased TSH
- C. Increased T3, T4, and increased TSH
- D. Decreased T3 and T4, increased TSH
Explanation: ***Increased T4, Increased T3, decreased TSH*** - In **primary hyperthyroidism**, the thyroid gland overproduces thyroid hormones (**T3 and T4**), leading to elevated levels [1]. - The high levels of T3 and T4 then **feedback negatively** on the pituitary gland, suppressing the release of **TSH** [1]. *Increased T4, normal T3, and increased TSH* - This pattern is inconsistent with primary hyperthyroidism, as elevated T3 and T4 should suppress TSH. - An isolated increase in T4 with normal T3 can occur in **subclinical hyperthyroidism** or **thyroxine (T4) resistance**, but increased TSH would suggest pituitary dysfunction or resistance to thyroid hormones. *Increased T3, T4, and increased TSH* - Elevated T3 and T4 accompanied by **increased TSH** is a rare presentation, usually indicating **TSH-secreting pituitary adenoma** (secondary hyperthyroidism) or **thyroid hormone resistance** [1], [2]. - In typical hyperthyroidism, high thyroid hormone levels would suppress TSH. *Decreased T3 and T4, increased TSH* - This profile is characteristic of **primary hypothyroidism**, where an underactive thyroid gland produces insufficient T3 and T4 [1]. - The low thyroid hormone levels stimulate the pituitary to release **more TSH** in an attempt to stimulate thyroid hormone production [1].
Question 5: Adrenal reserve is best tested by means of infusion with
- A. ACTH (Correct Answer)
- B. Metyrapone
- C. Corticosteroids
- D. LHRH
Explanation: ACTH - The **ACTH stimulation test**, also known as the **cosyntropin test**, is the most common dynamic test for assessing adrenal reserve. - Exogenous ACTH (cosyntropin) stimulates the adrenal glands to produce cortisol; a subnormal response indicates adrenal insufficiency. *Corticosteroids* - **Corticosteroids** are hormones (like cortisol) produced by the adrenal glands, or synthetic versions used as medications; they do not test adrenal reserve but rather *replace* adrenal function. - Administering corticosteroids would interfere with, rather than assess, the adrenal gland's ability to produce its own hormones. *LHRH* - **Luteinizing hormone-releasing hormone (LHRH)** is used to assess the function of the anterior pituitary gland and gonads, not the adrenal glands. - An LHRH stimulation test evaluates the pituitary's ability to release LH and FSH, which in turn stimulate gonadal hormone production. *Metyrapone* - The **metyrapone test** assesses the integrity of the **hypothalamic-pituitary-adrenal axis** by blocking cortisol synthesis, which should lead to an increase in ACTH and 11-deoxycortisol [1]. - While it evaluates a part of adrenal function, it is primarily used to differentiate between primary and secondary adrenal insufficiency, and not a direct measure of cortisol production capacity in response to stimulation.
Question 6: A 45-year-old man with a recent history of bizarre behavior is seen by a psychiatrist. On physical examination, the patient appears moderately obese with mild hypertension, facial acne, and fat accumulation in the supraclavicular fossae. Laboratory studies demonstrate neutrophilic leukocytosis, decreased lymphocytes, and absence of eosinophils, along with mild hypokalemia and mild metabolic alkalosis. The fasting serum glucose is within the reference range, but the OGTT shows glucose concentrations > 200 mg/dL. Laboratory studies also show a free urinary cortisol of 156 mg/24 hours. Which of the following questions would be of most help in establishing a diagnosis?
- A. Are you experiencing muscle weakness?
- B. Do you have a family history of endocrine neoplasia?
- C. Are you experiencing shortness of breath?
- D. Are you receiving corticosteroids for some other disease? (Correct Answer)
Explanation: ***Are you receiving corticosteroids for some other disease?*** - The patient's presentation including **obesity**, **hypertension**, **facial acne**, **supraclavicular fat accumulation** (buffalo hump), **neutrophilic leukocytosis**, **lymphopenia**, **eosinopenia**, **hypokalemia**, **metabolic alkalosis**, and **impaired glucose tolerance** with **elevated urinary free cortisol** are all highly suggestive of **Cushing's syndrome** [1]. - Exogenous corticosteroid use is the most common cause of Cushing's syndrome (iatrogenic Cushing's syndrome), and directly asking about it is crucial to differentiate it from endogenous causes [2]. *Are you experiencing muscle weakness?* - **Proximal muscle weakness** is a common symptom in Cushing's syndrome due to the catabolic effects of excess cortisol on muscle protein [1]. - While it's a helpful diagnostic symptom, it describes a manifestation of the disease rather than helping to determine its etiology, especially when differentiating between endogenous and exogenous causes. *Are you experiencing shortness of breath?* - **Shortness of breath** is not a direct or common symptom of Cushing's syndrome itself. - While hypertension and obesity associated with Cushing's can contribute to cardiovascular or respiratory issues in some cases, it's not a primary or specific finding. *Do you have a family history of endocrine neoplasia?* - A family history of **endocrine neoplasia** (e.g., Multiple Endocrine Neoplasia type 1 or 2, or familial isolated pituitary adenoma) might suggest an inherited predisposition to certain endocrine tumors, some of which could potentially cause endogenous Cushing's syndrome (e.g., pituitary adenoma leading to ACTH-dependent Cushing's disease) [3]. - However, considering the overall clinical picture, the initial step should be to rule out the most common cause of Cushing's symptoms, which is exogenous corticosteroid use, before delving into rare genetic causes of endogenous Cushing's.
Question 7: The following is a histopathological image of thyroid pathology. What is the diagnosis?
- A. Papillary carcinoma of thyroid
- B. Medullary carcinoma of thyroid (Correct Answer)
- C. Follicular carcinoma of thyroid
- D. Anaplastic carcinoma of thyroid
Explanation: ***Medullary carcinoma of thyroid*** - This image shows sheets and nests of **polygonal to spindle-shaped cells**, which are characteristic of medullary thyroid carcinoma, especially when mixed with an **amyloid stroma** (seen as amorphous eosinophilic material) [2]. - The presence of **neuroendocrine features** and the production of **calcitonin** are hallmarks of these C-cell tumors [1], [2]. *Papillary carcinoma of thyroid* - Characterized by **papillary architecture**, **ground-glass (Orphan Annie eye) nuclei**, nuclear grooves, and intranuclear cytoplasmic inclusions. - These features are not prominently seen in the provided image. *Follicular carcinoma of thyroid* - Defined by an invasive growth pattern of **well-differentiated follicular cells** forming follicles, with either capsular or vascular invasion [2]. - The image does not show classic follicular architectural patterns or clear evidence of invasion in the absence of a capsule. *Anaplastic carcinoma of thyroid* - This is a highly aggressive and undifferentiated tumor with **marked pleomorphism**, bizarre giant cells, and high mitotic activity [2]. - While there is some pleomorphism, the overall pattern and cellular morphology in the image are more consistent with medullary carcinoma than the extreme anaplasia. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1102-1103. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 428-431.
Question 8: False regarding Alzheimer's disease (AD) is:
- A. Number of neurofibrillary tangles is associated with the severity of dementia
- B. Number of senile (neuritic) plaques correlates (increases) with age
- C. Presence of tau protein suggest neurodegeneration
- D. Extracellular inclusion (lesion) can occur in the absence of intracellular inclusions to make pathological diagnosis of AD (Correct Answer)
Explanation: ***Extracellular inclusion (lesion) can occur in the absence of intracellular inclusions to make pathological diagnosis of AD*** - A definitive pathological diagnosis of **Alzheimer's disease** requires both the presence of **extracellular amyloid plaques** and **intracellular neurofibrillary tangles** [1]. - Neither inclusion type alone is sufficient for the diagnosis, as amyloid plaques can be found in non-demented elderly individuals [1]. *Number of neurofibrillary tangles is associated with the severity of dementia* - The **density and distribution of neurofibrillary tangles** (NFTs) directly correlate with the severity of cognitive impairment and **dementia** in AD [1]. - Tangles are composed of hyperphosphorylated **tau protein** and disrupt neuronal function, leading to neurodegeneration [2]. *Number of senile (neuritic) plaques correlates (increases) with age* - The accumulation of **senile (neuritic) plaques**, composed primarily of **beta-amyloid protein**, generally increases with age, even in cognitively normal individuals [1]. - While plaques are a hallmark of AD, their mere presence is not always diagnostic of clinical dementia [1]. *Presence of tau protein suggest neurodegeneration* - The presence of **hyperphosphorylated tau protein**, especially when forming **neurofibrillary tangles**, is a strong indicator of **neurodegeneration** [2]. - **Tauopathy** is a key pathological feature in AD and other neurodegenerative diseases [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1292-1294. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 721-722.
Question 9: Which of the following is the most sensitive and specific initial laboratory test to diagnose iron deficiency?
- A. Serum iron levels
- B. Serum ferritin levels (Correct Answer)
- C. Serum transferrin receptor population
- D. Transferrin saturation
Explanation: ***Serum ferritin levels*** - **Serum ferritin** directly reflects the body's iron stores and is the **most sensitive and specific indicator of iron deficiency**, even before anemia develops [1]. - A low serum ferritin level (< 15-30 ng/mL) confirms **iron depletion** and distinguishes iron deficiency from other causes of microcytic anemia [1]. *Serum iron levels* - **Serum iron** fluctuates throughout the day and is affected by recent iron intake, making it less reliable for diagnosing iron deficiency compared to ferritin. - While typically low in iron deficiency, it can also be low in **anemia of chronic disease**, leading to false positives [2]. *Serum transferrin receptor population* - **Serum transferrin receptor (sTfR)** levels rise with iron deficiency as cells upregulate receptors to capture more iron. - While useful, especially in differentiating iron deficiency from **anemia of chronic disease**, it is generally less sensitive and specific than ferritin as an initial stand-alone test. *Transferrin saturation* - **Transferrin saturation** (calculated as serum iron / total iron-binding capacity) indicates the amount of iron bound to transferrin. - A low percentage suggests **iron deficiency**, but it can also be low in other conditions and is not as sensitive or specific as ferritin for initial diagnosis.
Question 10: Classical markers for Hodgkin's disease are
- A. CD 15 and CD 30 (Correct Answer)
- B. CD 15 and CD 20
- C. CD 20 and CD 30
- D. CD 15 and CD 22
Explanation: ***CD 15 and CD 30*** - These are **classical markers** specific for Reed-Sternberg cells, which are characteristic of Hodgkin's lymphoma [1][2]. - The presence of both markers is essential for **diagnosing Hodgkin's disease** and differentiating it from non-Hodgkin lymphomas [1]. *CD 20 and CD 30* - **CD 20** is primarily associated with B-cell non-Hodgkin lymphomas and is not a classical marker for Hodgkin's disease. - Hodgkin's lymphoma typically does not express **CD 20**, making this combination inappropriate for diagnosis. *CD 15 and CD 20* - While **CD 15** is a classical marker for Hodgkin's, **CD 20** is linked to B-lineage cells, which are not prominently present in Hodgkin's disease. - Diagnosis relies on the presence of **CD 30** alongside **CD 15**, highlighting the key difference. *CD 15 and CD 22* - Although **CD 15** is associated with Hodgkin's disease, **CD 22** is not a marker indicative of this lymphoma type. - **CD 22** is more relevant to B-cell malignancies; thus, it is not part of the classical markers for Hodgkin's lymphoma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 614-616. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 616.
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