Endocrine Pathology — MCQs

A 45-year-old man presents with a 3 cm palpable nodule in one lobe of an otherwise normal-sized thyroid gland. Needle aspiration of the nodule demonstrates polygonal tumor cells and amyloid, but only very scanty colloid and normal follicular cells. Which of the following is the most likely diagnosis?

Q117Easy

Ectopic ACTH syndrome is seen most commonly with which of the following conditions?

Q118Medium

Which of the following is the most reliable feature of malignant transformation of pheochromocytoma?

Q119Easy

The FNAC of the lesion should reveal:

Q120Medium

A 68-year-old man has experienced increasing malaise for 3 years. Physical examination shows no remarkable findings. Laboratory findings include a serum creatinine level of 4.9 mg/dL and a urea nitrogen level of 45 mg/dL. Abdominal CT scan shows small kidneys. Which of the following endocrine glandular lesions has developed secondary to the underlying disease in this patient?

Endocrine Pathology Indian Medical PG Practice Questions and MCQs

Question 111: Which of the following is not a feature of Papillary carcinoma of thyroid?

A. Rearrangement of RET gene
B. Rearrangement of NTRK1 gene
C. Mutation of BRAF gene
D. Mutation of RAS gene (Correct Answer)

Explanation: Papillary Thyroid Carcinoma (PTC) is the most common thyroid malignancy [1]. Its pathogenesis is primarily driven by the activation of the **MAPK (Mitogen-Activated Protein Kinase) pathway**. **Why "Mutation of RAS gene" is the correct answer:** While RAS mutations can occur in many thyroid tumors, they are characteristically associated with **Follicular Adenomas** and **Follicular Thyroid Carcinomas (FTC)**, as well as the follicular variant of PTC. However, in the context of classic Papillary Carcinoma, RAS mutations are not a defining feature. Instead, PTC is defined by specific rearrangements and BRAF mutations. **Analysis of Incorrect Options:** * **A. Rearrangement of RET gene:** Chromosomal rearrangements involving the RET proto-oncogene (forming **RET/PTC fusion genes**) are found in approximately 20-40% of PTCs, especially in cases associated with radiation exposure and in children [1]. * **B. Rearrangement of NTRK1 gene:** Similar to RET, rearrangements of the Nerve Growth Factor Receptor (NTRK1) are seen in a smaller subset (5-10%) of PTC cases. * **C. Mutation of BRAF gene:** This is the most common genetic alteration in PTC (seen in 40-60% of cases). The **V600E mutation** is highly specific for Papillary Carcinoma and is often associated with a higher risk of lymph node metastasis and extrathyroidal extension. **High-Yield Clinical Pearls for NEET-PG:** * **Psammoma bodies:** Laminated calcifications characteristic of PTC (not seen in Follicular Ca). * **Nuclear features (Diagnostic):** Orphan Annie eye nuclei (clearing), nuclear grooves, and pseudo-inclusions [2]. * **Spread:** PTC primarily spreads via **lymphatics** (Cervical lymph nodes), whereas Follicular Ca spreads **hematogenously** [2]. * **Prognosis:** Excellent, with a 10-year survival rate >95% [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1098-1099. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 429-430.

Question 112: What is the commonest cause of raised serum calcium?

A. Ectopic secretion
B. Parathyroid hyperplasia
C. Parathyroid adenoma (Correct Answer)
D. Parathyroid carcinoma

Explanation: **Explanation:** The most common cause of hypercalcemia in the **outpatient (ambulatory) setting** is **Primary Hyperparathyroidism (PHPT)** [1]. Among the causes of PHPT, a solitary **Parathyroid Adenoma** is the most frequent, accounting for approximately **85-90%** of cases [2]. It typically involves a single gland, while the remaining glands are normal or slightly atrophic due to feedback inhibition. **Analysis of Options:** * **B. Parathyroid Hyperplasia:** This involves all four parathyroid glands and accounts for about **10-15%** of PHPT cases. It is frequently associated with hereditary syndromes like MEN 1 and MEN 2A [1]. * **A. Ectopic Secretion:** This refers to the secretion of Parathyroid Hormone-related Protein (PTHrP) by malignant tumors (e.g., squamous cell carcinoma of the lung). While malignancy is the most common cause of hypercalcemia in **hospitalized patients**, it is less common overall than adenomas [1]. * **D. Parathyroid Carcinoma:** This is an extremely rare cause, accounting for **<1%** of PHPT cases. It is characterized by very high calcium levels and a palpable neck mass. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad of PHPT:** "Stones (renal calculi), bones (osteitis fibrosa cystica), abdominal groans (peptic ulcers/pancreatitis), and psychic overtones (depression)." [3] * **Biochemical Profile:** ↑ Serum Calcium, ↓ Serum Phosphate, and ↑ PTH. * **Morphology:** On histopathology, adenomas are usually hypercellular and lack stromal fat, often showing a rim of normal parathyroid tissue at the periphery. * **Most common gene mutation:** *Cyclin D1* (PRAD1) overexpression or *MEN1* mutations. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 667-668. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 127-128. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1105-1106.

Question 113: MEN syndrome is associated with an increase in which type of thyroid carcinoma?

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 (MTC)** is the correct answer because it is a defining component of **Multiple Endocrine Neoplasia (MEN) type 2 syndromes (2A and 2B)** [1]. MTC originates from the **parafollicular C-cells**, which are neuroendocrine cells derived from the neural crest that secrete calcitonin [2]. In the context of MEN 2, MTC is typically multifocal, bilateral, and preceded by C-cell hyperplasia. It is associated with germline mutations in the **RET proto-oncogene** [1]. **Analysis of Incorrect Options:** * **Papillary Carcinoma (A):** The most common thyroid cancer overall, associated with *BRAF* mutations and radiation exposure, but not typically part of MEN syndromes. * **Follicular Carcinoma (B):** Associated with iodine deficiency and *RAS* mutations/PAX8-PPARγ rearrangements; it does not have a genetic link to MEN. * **Anaplastic Carcinoma (D):** A highly aggressive, undifferentiated tumor seen in older patients; it is not associated with the inherited MEN syndromes. **High-Yield Clinical Pearls for NEET-PG:** * **MEN 2A (Sipple Syndrome):** MTC + Pheochromocytoma + Parathyroid Hyperplasia [1]. * **MEN 2B (Wagenmann-Froboese):** MTC + Pheochromocytoma + Mucosal Neuromas + Marfanoid Habitus [1]. * **Tumor Marker:** Calcitonin is used for diagnosis and monitoring recurrence [2]. Amyloid stroma (formed by calcitonin pro-peptides) is a classic histological finding [3]. * **Prophylactic Thyroidectomy:** Recommended for children carrying the *RET* mutation before MTC develops. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, p. 1137. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 428-429. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 430-431.

Question 114: Psammoma bodies are seen in which of the following conditions?

A. Papillary carcinoma of thyroid (Correct Answer)
B. Medullary carcinoma of thyroid
C. Follicular carcinoma of thyroid
D. Anaplastic carcinoma of thyroid

Explanation: **Explanation:** **1. Why Option A is Correct:** Psammoma bodies are a hallmark histopathological feature of **Papillary Carcinoma of the Thyroid (PTC)**, occurring in approximately 40–50% of cases. They are round, concentric, laminated calcifications that represent the infarction and subsequent calcification of the tips of the papillae [1], [3]. In the context of thyroid pathology, their presence is highly suggestive of PTC, even if found in cervical lymph nodes [2]. **2. Why the Other Options are Incorrect:** * **Medullary Carcinoma (MTC):** Characterized by nests of polygonal cells in a fibrovascular stroma containing **Amyloid deposits** (derived from calcitonin). While focal calcification can occur, laminated Psammoma bodies are not characteristic [2]. * **Follicular Carcinoma:** This tumor is characterized by follicles and a thick capsule with vascular or capsular invasion [2]. It typically lacks both papillae and Psammoma bodies. * **Anaplastic Carcinoma:** This is a highly aggressive, undifferentiated tumor showing pleomorphic giant cells or spindle cells [2]. It does not form the organized papillary structures required to produce Psammoma bodies. **3. NEET-PG High-Yield Clinical Pearls:** * **Mnemonic for Psammoma Bodies (PSaMMoma):** **P**apillary CA (Thyroid/Renal/Serous Ovarian), **S**erous Cystadenocarcinoma of Ovary, **M**eningioma, **M**esothelioma [3]. * **Nuclear Features of PTC:** For NEET-PG, remember that nuclear findings are more diagnostic than Psammoma bodies. Look for **Orphan Annie eye nuclei** (optically clear), **Pseudo-inclusions**, and **Nuclear grooves** [1], [2]. * **Genetic Association:** PTC is frequently associated with **BRAF mutations** (V600E) and **RET/PTC rearrangements**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, p. 1099. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 429-430. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 134-135.

Question 115: A patient presents with increased metabolic rate, hyperthyroidism, and goiter. Deposits of calcium are noted in the thyroid capsule. What is the likely diagnosis?

A. Follicular Carcinoma of the thyroid
B. Medullary carcinoma of the thyroid (Correct Answer)
C. De Quervain's thyroiditis
D. Riedel's thyroiditis

Explanation: ### Explanation **Correct Answer: B. Medullary Carcinoma of the Thyroid (MTC)** Medullary carcinoma of the thyroid arises from the **para-follicular C-cells**, which secrete **calcitonin** [1]. While calcitonin typically lowers serum calcium, its excessive secretion in MTC can lead to **dystrophic calcification** within the tumor stroma. A classic histopathological hallmark of MTC is the presence of **amyloid deposits** (derived from pro-calcitonin), which frequently undergo calcification [2]. When these deposits occur in the thyroid capsule or stroma, they appear as radiopaque or gritty areas. Furthermore, MTC can be associated with MEN 2A/2B syndromes, which may present with hypermetabolic states (though the hyperthyroidism in this specific question stem is a distractor or related to associated MEN-related pheochromocytoma/hyperparathyroidism) [1]. **Why Incorrect Options are Wrong:** * **Follicular Carcinoma:** Characterized by capsular and vascular invasion [3]. While it can show calcification, it lacks the specific association with amyloid-driven calcification seen in MTC. * **De Quervain’s Thyroiditis:** A subacute granulomatous thyroiditis typically following a viral infection. It presents with a **painful** thyroid and transient hyperthyroidism, but not capsular calcium deposits. * **Riedel’s Thyroiditis:** Characterized by dense **"rock-hard" fibrosis** that extends beyond the thyroid capsule into adjacent neck structures. It mimics malignancy but is an IgG4-related systemic disease, not primarily a calcifying process. **NEET-PG High-Yield Pearls:** * **Stain for Amyloid:** Congo Red (shows **apple-green birefringence** under polarized light). * **Tumor Marker:** Calcitonin (used for diagnosis and monitoring recurrence) and CEA [1]. * **Genetics:** Strongly associated with **RET proto-oncogene** mutations. * **Psammoma Bodies:** These are characteristic of **Papillary** Thyroid Carcinoma, not Medullary. MTC has irregular calcified amyloid, not laminated psammoma bodies. **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. 430-431. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1100-1101.

Question 116: A 45-year-old man presents with a 3 cm palpable nodule in one lobe of an otherwise normal-sized thyroid gland. Needle aspiration of the nodule demonstrates polygonal tumor cells and amyloid, but only very scanty colloid and normal follicular cells. Which of the following is the most likely diagnosis?

A. Follicular thyroid carcinoma
B. Hashimoto's disease
C. Medullary thyroid carcinoma (Correct Answer)
D. Papillary thyroid carcinoma

Explanation: **Explanation:** The presence of **polygonal tumor cells** and **amyloid** on Fine Needle Aspiration (FNA) is pathognomonic for **Medullary Thyroid Carcinoma (MTC)** [1]. MTC arises from the parafollicular C-cells, which secrete calcitonin [1]. This calcitonin undergoes misfolding to form pro-amyloid, which stains positive with Congo Red (showing apple-green birefringence). Unlike follicular-derived tumors, MTC lacks significant colloid and follicular architecture [1]. **Analysis of Incorrect Options:** * **Follicular Thyroid Carcinoma (A):** Characterized by follicular cells arranged in microfollicles [3]. It lacks amyloid and typically shows abundant or altered colloid. FNA cannot distinguish it from a follicular adenoma; capsular/vascular invasion is required. * **Hashimoto's Disease (B):** An autoimmune condition presenting with diffuse enlargement (not usually a solitary nodule). Cytology shows Hurthle cells (oncocytes) and a dense lymphocytic infiltrate with germinal centers. * **Papillary Thyroid Carcinoma (D):** The most common thyroid cancer. Key features include Orphan Annie eye nuclei, nuclear grooves, intranuclear inclusions, and **Psammoma bodies** (laminated calcifications), not amyloid. **NEET-PG High-Yield Pearls:** * **Origin:** Parafollicular C-cells (Neuroendocrine) [1]. * **Marker:** Serum **Calcitonin** (used for diagnosis and monitoring recurrence) and CEA [2]. * **Genetics:** Associated with **RET proto-oncogene** mutations. * **Syndromes:** 20-25% are familial, occurring in **MEN 2A and 2B** [2]. * **Staining:** Amyloid stains with **Congo Red**; tumor cells are positive for Chromogranin and Synaptophysin. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 430-431. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1102-1103. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 428-429.

Question 117: Ectopic ACTH syndrome is seen most commonly with which of the following conditions?

A. Renal cell carcinoma
B. Lymphoma
C. Bronchogenic carcinoma (Correct Answer)
D. Pituitary adenoma

Explanation: **Explanation:** **Ectopic ACTH Syndrome** occurs when non-pituitary tumors secrete adrenocorticotropic hormone (ACTH) or its precursors, leading to ACTH-dependent Cushing syndrome [1]. **Why Bronchogenic Carcinoma is Correct:** The most common cause of ectopic ACTH production is **Small Cell Carcinoma of the Lung** (a type of bronchogenic carcinoma), accounting for approximately 50% of cases [1]. These neuroendocrine tumors possess the cellular machinery to synthesize and secrete polypeptide hormones like ACTH. Other common sources include bronchial carcinoids, medullary thyroid carcinoma, and pancreatic islet cell tumors. **Analysis of Incorrect Options:** * **Renal Cell Carcinoma (RCC):** While RCC is a classic "great imitator" known for paraneoplastic syndromes, it most commonly secretes **Erythropoietin** (leading to polycythemia) or **PTHrP** (leading to hypercalcemia) [2], not ACTH. * **Lymphoma:** Although rare cases exist, lymphomas are not a classic or common source of ectopic ACTH. * **Pituitary Adenoma:** This is the cause of **Cushing Disease**. While it involves high ACTH, it is considered "eutopic" (originating from the normal site) rather than "ectopic." **High-Yield Clinical Pearls for NEET-PG:** * **Cushing Disease vs. Ectopic ACTH:** In Ectopic ACTH syndrome, ACTH levels are typically **very high**, and unlike pituitary adenomas, the secretion is **not suppressed** by high-dose dexamethasone. * **Clinical Presentation:** Patients with ectopic ACTH (especially from Small Cell Lung Cancer) often present with rapid onset, severe **hypokalemic metabolic alkalosis**, and **hyperpigmentation** (due to MSH-like activity of ACTH precursors) [1], rather than the classic centripetal obesity seen in chronic Cushing’s. * **Most common cause of Cushing Syndrome overall:** Exogenous (iatrogenic) glucocorticoids. * **Most common endogenous cause:** Cushing Disease (Pituitary adenoma). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 421-423. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 338-339.

Question 118: Which of the following is the most reliable feature of malignant transformation of pheochromocytoma?

A. Presence of mitotic figures
B. Capsular invasion
C. Vascular invasion (Correct Answer)
D. Pleomorphism

Explanation: The diagnosis of malignancy in **Pheochromocytoma** is unique and often challenging in pathology. Unlike many other tumors, cellular features of "atypia" do not necessarily correlate with clinical behavior [1]. **Why Vascular Invasion is Correct:** In Pheochromocytoma, malignancy is defined strictly by the **presence of metastases** (spread to non-chromaffin sites like lungs, liver, or bone) or extensive **vascular/capsular invasion**. Among the options provided, **vascular invasion** is a definitive hallmark of malignant potential, as it indicates the tumor's ability to enter the systemic circulation and seed distant sites. **Why the Other Options are Incorrect:** * **A. Presence of mitotic figures:** While increased mitosis can be seen in aggressive tumors, it is not a standalone criterion for malignancy in pheochromocytoma. * **B. Capsular invasion:** While a feature of malignancy, it is often considered less definitive than vascular invasion or distant metastasis in this specific tumor type. * **D. Pleomorphism:** This is the most important "trap" in endocrine pathology. Benign pheochromocytomas often exhibit significant nuclear pleomorphism and hyperchromasia (known as "endocrine atypia") [1]. Therefore, cellular appearance alone cannot distinguish benign from malignant lesions. **NEET-PG High-Yield Pearls:** * **Rule of 10s:** 10% are malignant, 10% are bilateral, 10% are extra-adrenal (Paragangliomas), and 10% occur in children. * **Zellballen Pattern:** The classic histological arrangement of tumor cells in nests surrounded by sustentacular cells. * **PASS Score:** The *Pheochromocytoma of the Adrenal Gland Scaled Score* is used to predict malignant potential, but clinical metastasis remains the only absolute proof. * **Genetic Association:** Strongly linked with **MEN 2A/2B**, VHL syndrome, and NF-1 [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 419-420. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, p. 1137.

Question 119: The FNAC of the lesion should reveal:

A. ‘Orphan-Annie eye’ nucleus cells (Correct Answer)
B. Amyloid deposits
C. Epithelioid cells and giant cells
D. Follicular cells

Explanation: ***'Orphan-Annie eye' nucleus cells*** - **'Orphan-Annie eye' nuclei** are the pathognomonic cytological feature of **papillary thyroid carcinoma (PTC)** on FNAC, appearing as large, pale, ground-glass nuclei with cleared chromatin. - Other key PTC nuclear features include **nuclear grooves**, **intranuclear pseudoinclusions**, and occasional **psammoma bodies**. *Amyloid deposits* - **Amyloid deposits** are characteristic of **medullary thyroid carcinoma**, not papillary thyroid carcinoma. - Medullary carcinoma arises from **C-cells** and secretes **calcitonin**, showing **Congo red positivity** for amyloid. *Epithelioid cells and giant cells* - **Epithelioid cells** and **giant cells** are typical of **granulomatous thyroiditis** (de Quervain's thyroiditis) or **chronic lymphocytic thyroiditis**. - These inflammatory cells are not characteristic features of **papillary thyroid carcinoma**. *Follicular cells* - **Follicular cells** alone are seen in **follicular neoplasms** or **normal thyroid tissue**, lacking the specific nuclear features of PTC. - **Follicular carcinoma** requires **histological examination** to demonstrate **capsular** or **vascular invasion**, not distinguishable on FNAC.

Question 120: A 68-year-old man has experienced increasing malaise for 3 years. Physical examination shows no remarkable findings. Laboratory findings include a serum creatinine level of 4.9 mg/dL and a urea nitrogen level of 45 mg/dL. Abdominal CT scan shows small kidneys. Which of the following endocrine glandular lesions has developed secondary to the underlying disease in this patient?

A. Adrenal atrophy
B. Islet cell hyperplasia
C. Multinodular goiter
D. Parathyroid hyperplasia (Correct Answer)

Explanation: **Explanation:** The patient presents with chronic kidney disease (CKD), evidenced by elevated creatinine (4.9 mg/dL), elevated BUN, and bilateral small (atrophic) kidneys. This clinical scenario leads to **Secondary Hyperparathyroidism.** [1] **Mechanism:** In CKD, the kidneys fail to excrete phosphate (hyperphosphatemia) and cannot adequately convert Vitamin D to its active form, 1,25-(OH)₂D₃ (calcitriol). [1] This results in hypocalcemia. The persistent low serum calcium and high phosphate levels act as potent stimuli for the parathyroid glands. [2] In an attempt to restore calcium homeostasis, all four parathyroid glands undergo **diffuse or nodular hyperplasia** to secrete more Parathyroid Hormone (PTH). [3] **Why Incorrect Options are Wrong:** * **Adrenal atrophy:** Usually results from exogenous steroid use or pituitary failure (secondary hypocortisolism). It is not a consequence of renal failure. * **Islet cell hyperplasia:** This is typically seen in neonates of diabetic mothers or as part of MEN1 syndrome, not CKD. * **Multinodular goiter:** This is related to iodine deficiency or biosynthetic defects in thyroid hormone production, unrelated to renal pathology. **NEET-PG High-Yield Pearls:** * **Renal Osteodystrophy:** The collective bone changes (osteitis fibrosa cystica, osteomalacia) resulting from secondary hyperparathyroidism in CKD. [2] * **Tertiary Hyperparathyroidism:** Occurs when parathyroid hyperplasia becomes autonomous after long-standing secondary hyperparathyroidism, leading to hypercalcemia (often seen post-renal transplant). * **Lab Profile in Secondary HPT:** ↓ Serum Calcium, ↑ Serum Phosphate, ↑ Serum PTH, and ↓ Vitamin D levels. [1] **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1106-1107. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1194-1195. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 667-668.

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