Calcium Homeostasis (DS)

Question: What is the primary stimulus for the secretion of Parathyroid Hormone (PTH)?

A) Hypercalcemia
B) Hypocalcemia
C) Hyperphosphatemia
D) Hypophosphatemia

Answer: B) Hypocalcemia

Question: Which cells are responsible for the production and secretion of Parathyroid Hormone?

A) Oxyphil cells
B) Parafollicular cells
C) Chief cells
D) Follicular cells

Answer: C) Chief cells

Question: Through which secondary messenger system does PTH primarily operate in its target cells?

A) IP3
B) Diacylglycerol
C) cGMP
D) cAMP

Answer: D) cAMP

Question: PTH binding to osteoblasts leads to bone resorption by stimulating the expression of what?

A) Osteoprotegerin (OPG)
B) RANK Ligand (RANKL)
C) Calcitonin
D) Calcitriol

Answer: B) RANK Ligand (RANKL)

Question: What is the role of Osteoprotegerin (OPG) in bone metabolism?

A) It activates osteoclast precursors.
B) It inhibits RANKL-induced bone resorption.
C) It directly stimulates osteoblast activity.
D) It converts calcidiol to calcitriol.

Answer: B) It inhibits RANKL-induced bone resorption.

Question: In the kidney, PTH increases calcium reabsorption primarily in which segments?

A) Proximal Convoluted Tubule
B) Glomerulus
C) Thick Ascending Limb and Distal Convoluted Tubule
D) Collecting Duct

Answer: C) Thick Ascending Limb and Distal Convoluted Tubule

Question: The active form of Vitamin D, which increases intestinal calcium absorption, is called:

A) Cholecalciferol
B) Calcidiol
C) Calcitriol
D) Ergocalciferol

Answer: C) Calcitriol

Question: How does PTH indirectly increase intestinal calcium absorption?

A) By binding directly to intestinal receptors
B) By stimulating the release of gastrin
C) By promoting the formation of calcitriol
D) By decreasing renal phosphate excretion

Answer: C) By promoting the formation of calcitriol

Question: The Calcium-Sensing Receptor (CaSR) in the parathyroid gland inhibits PTH release in response to:

A) Low plasma calcium
B) High plasma calcium
C) Low plasma phosphate
D) High plasma phosphate

Answer: B) High plasma calcium

Question: Which intracellular signaling molecules are activated by the Calcium-Sensing Receptor (CaSR) to inhibit PTH release?

A) cAMP and Protein Kinase A
B) IP3 and Diacylglycerol
C) cGMP and Nitric Oxide
D) JAK and STAT

Answer: B) IP3 and Diacylglycerol

Question: What is the preferred laboratory method for measuring bio-intact PTH?

A) Radioimmunoassay
B) Two-site chemiluminescent assay
C) ELISA
D) Western Blot

Answer: B) Two-site chemiluminescent assay

Question: PTH-related peptide (PTHrP) is most commonly associated with hypercalcemia in which cancers?

A) Prostate and Colon
B) Breast and Lung
C) Thyroid and Adrenal
D) Pancreatic and Bladder

Answer: B) Breast and Lung

Question: In a lactating mother, what hormone is produced by the mammary gland in response to low calcium to help mobilize calcium for milk?

A) Parathyroid Hormone (PTH)
B) Prolactin
C) PTH-related peptide (PTHrP)
D) Calcitonin

Answer: C) PTH-related peptide (PTHrP)

Question: Which of the following is NOT a classic characteristic of Vitamin D?

A) It is a true vitamin that must be obtained solely from the diet.
B) It is a lipid-soluble hormone.
C) It acts on distant target cells via intracellular receptors.
D) Its carrier protein is vitamin D-binding protein.

Answer: A) It is a true vitamin that must be obtained solely from the diet.

Question: The major circulating and storage form of Vitamin D is:

A) Calcitriol
B) Cholecalciferol
C) Calcidiol
D) Ergocalciferol

Answer: C) Calcidiol

Question: Which enzyme, upregulated by PTH, converts calcidiol to calcitriol in the kidney?

A) 25-hydroxylase
B) 1-alpha-hydroxylase
C) 24-hydroxylase
D) 7-dehydrocholesterol reductase

Answer: B) 1-alpha-hydroxylase

Question: What effect does Vitamin D have on intestinal calcium absorption?

A) It decreases the production of calbindin.
B) It inhibits calcium transporters.
C) It increases the production of calbindin.
D) It has no direct effect on the intestine.

Answer: C) It increases the production of calbindin.

Question: Which hormone is secreted by the parafollicular cells (C cells) of the thyroid gland and acts to lower blood calcium?

A) Parathyroid Hormone
B) Thyroxine
C) Calcitonin
D) Triiodothyronine

Answer: C) Calcitonin

Question: The primary physiological role of calcitonin in humans is considered to be:

A) Powerful regulation of plasma calcium compared to PTH.
B) Inhibition of bone resorption by osteoclasts.
C) Stimulation of calcium reabsorption in the kidney.
D) Major stimulation of intestinal calcium absorption.

Answer: B) Inhibition of bone resorption by osteoclasts.

Question: In clinical practice, calcitonin is primarily measured as a tumor marker for which condition?

A) Papillary Thyroid Carcinoma
B) Medullary Thyroid Carcinoma
C) Graves' Disease
D) Hashimoto's Thyroiditis

Answer: B) Medullary Thyroid Carcinoma

Question: Which test is preferred and more sensitive for stimulating calcitonin release in the diagnosis of Medullary Thyroid Carcinoma?

A) Calcium Stimulation Test
B) Pentagastrin Stimulation Test
C) TRH Stimulation Test
D) ACTH Stimulation Test

Answer: B) Pentagastrin Stimulation Test

Question: A peak calcitonin level of >100 ng/L after a Pentagastrin stimulation test is interpreted as:

A) Normal for most adults
B) Possible MTC or other thyroid pathology
C) Probable MTC
D) C-cell hyperplasia only

Answer: C) Probable MTC

Question: Procalcitonin is used clinically as a biomarker for:

A) Primary Hyperparathyroidism
B) Early detection of systemic bacterial infections or sepsis
C) Vitamin D deficiency
D) Familial Hypocalciuric Hypercalcemia

Answer: B) Early detection of systemic bacterial infections or sepsis

Question: What is the most common cause of hypercalcemia?

A) Vitamin D intoxication
B) Primary Hyperparathyroidism
C) Milk-alkali syndrome
D) Lithium therapy

Answer: B) Primary Hyperparathyroidism

Question: Osteitis Fibrosa Cystica is a unique bone manifestation associated with:

A) Hypoparathyroidism
B) Primary Hyperparathyroidism
C) Vitamin D Deficiency
D) Medullary Thyroid Carcinoma

Answer: B) Primary Hyperparathyroidism

Question: Humoral Hypercalcemia of Malignancy, without bony metastases, is often caused by tumor production of:

A) Parathyroid Hormone (PTH)
B) Calcitonin
C) PTH-related peptide (PTHrP)
D) Active Vitamin D

Answer: C) PTH-related peptide (PTHrP)

Question: Vitamin D intoxication (Hypervitaminosis D) leads to hypercalcemia because:

A) It directly inhibits PTH secretion.
B) Calcitriol has functions similar to PTH, increasing blood calcium.
C) It destroys osteoclasts.
D) It blocks calcium absorption in the gut.

Answer: B) Calcitriol has functions similar to PTH, increasing blood calcium.

Question: In granulomatous disorders like sarcoidosis, hypercalcemia can occur due to:

A) Ectopic PTH production
B) Unregulated generation of calcitriol by macrophages
C) Massive bone metastases
D) Autoimmune destruction of the parathyroid gland

Answer: B) Unregulated generation of calcitriol by macrophages

Question: Familial Hypocalciuric Hypercalcemia is characterized by a mutation in the gene for:

A) The Parathyroid Hormone receptor
B) The Vitamin D receptor
C) The Calcium-Sensing Receptor (CaSR)
D) The RANK Ligand

Answer: C) The Calcium-Sensing Receptor (CaSR)

Question: A hallmark laboratory finding in Familial Hypocalciuric Hypercalcemia is:

A) High urinary calcium and high blood calcium
B) Low urinary calcium and high blood calcium
C) High urinary calcium and low blood calcium
D) Low urinary calcium and low blood calcium

Answer: B) Low urinary calcium and high blood calcium

Question: Which of the following is a cause of hypocalcemia?

A) Primary Hyperparathyroidism
B) Vitamin D Intoxication
C) Hypoparathyroidism
D) Lithium Therapy

Answer: C) Hypoparathyroidism

Question: DiGeorge syndrome is an example of hypoparathyroidism caused by:

A) Autoimmune destruction
B) Defective embryologic development of the parathyroid glands
C) Synthesis of biologically inactive PTH
D) PTH receptor resistance

Answer: B) Defective embryologic development of the parathyroid glands

Question: In Pseudohypoparathyroidism, the primary defect is:

A) The parathyroid glands fail to produce PTH.
B) The body fails to respond to PTH due to a receptor defect.
C) There is excessive degradation of PTH.
D) Vitamin D is not converted to its active form.

Answer: B) The body fails to respond to PTH due to a receptor defect.

Question: Hypovitaminosis D has become more common partly due to:

A) Excessive sun exposure
B) Over-supplementation of Vitamin D
C) Fear of skin cancer leading to sun avoidance
D) Increased consumption of fatty fish

Answer: C) Fear of skin cancer leading to sun avoidance

Question: The failure to mineralize newly formed organic bone matrix in adults is called:

A) Rickets
B) Osteoporosis
C) Osteomalacia
D) Osteitis Fibrosa Cystica

Answer: C) Osteomalacia

Question: In children, Vitamin D deficiency before the cessation of growth leads to:

A) Osteoporosis
B) Osteomalacia
C) Rickets
D) Medullary Thyroid Carcinoma

Answer: C) Rickets

Question: Which test is used to measure Bone Mineral Density?

A) Serum Calcitonin level
B) PTH level
C) Dual-Energy X-ray Absorptiometry (DXA)
D) Pentagastrin Stimulation Test

Answer: C) Dual-Energy X-ray Absorptiometry (DXA)

Question: Chvostek's sign, a indicator of hypocalcemia, involves tapping which cranial nerve?

A) CN V (Trigeminal)
B) CN VII (Facial)
C) CN X (Vagus)
D) CN XII (Hypoglossal)

Answer: B) CN VII (Facial)

Question: A positive Trousseau's sign is indicated by:

A) Facial twitching upon tapping
B) Carpopedal spasm after inflation of a blood pressure cuff
C) Bowing of the legs
D) A rachitic rosary on the chest

Answer: B) Carpopedal spasm after inflation of a blood pressure cuff

Question: Which hormone is the primary regulator of plasma calcium levels?

A) Calcitonin
B) Parathyroid Hormone
C) Thyroxine
D) Insulin

Answer: B) Parathyroid Hormone

Question: Where are the parathyroid glands located?

A) Within the thyroid gland itself
B) On the posterior surface of the thyroid gland
C) In the mediastinum near the heart
D) On the superior poles of the kidneys

Answer: B) On the posterior surface of the thyroid gland

Question: The conversion of 7-dehydrocholesterol to cholecalciferol occurs in the:

A) Liver
B) Kidney
C) Skin upon exposure to UV light
D) Intestine

Answer: C) Skin upon exposure to UV light

Question: Cutaneous production of Vitamin D is decreased by:

A) High levels of melanin
B) Low SPF sunblock
C) High ambient temperature
D) High humidity

Answer: A) High levels of melanin

Question: Which form of Vitamin D is measured to assess nutritional Vitamin D status?

A) Calcitriol
B) Calcidiol
C) Cholecalciferol
D) Ergocalciferol

Answer: B) Calcidiol

Question: The main effect of Vitamin D on the kidney is:

A) Major increase in calcium reabsorption
B) Major increase in phosphate excretion
C) Minor decrease in calcium and phosphate excretion
D) Stimulation of 1-alpha-hydroxylase

Answer: C) Minor decrease in calcium and phosphate excretion

Question: Calcitonin's action in the kidney leads to:

A) Increased calcium reabsorption
B) Decreased calcium reabsorption
C) Increased phosphate reabsorption
D) Activation of Vitamin D

Answer: B) Decreased calcium reabsorption

Question: A patient with high serum calcium and normal PTH levels should be suspected of having:

A) Primary Hyperparathyroidism
B) Hypoparathyroidism
C) PTH-related peptide production
D) Vitamin D deficiency

Answer: C) PTH-related peptide production

Question: Which condition is characterized by low blood calcium and high blood phosphate?

A) Primary Hyperparathyroidism
B) Hypervitaminosis D
C) Pseudohypoparathyroidism
D) Familial Hypocalciuric Hypercalcemia

Answer: C) Pseudohypoparathyroidism

Question: The synthesis of procalcitonin can be massively increased by:

A) Hypocalcemia
B) Circulating endotoxins or cytokines from bacterial infection
C) Hypercalcemia
D) PTH secretion

Answer: B) Circulating endotoxins or cytokines from bacterial infection

Question: In a normal thyroid gland, what is secreted?

A) PTH and Calcitonin
B) Only Calcitonin
C) Only PTH
D) T3, T4, and Calcitonin

Answer: D) T3, T4, and Calcitonin

Question: The primary function of RANKL (RANK Ligand) is to:

A) Inhibit osteoclast activity
B) Activate osteoblast activity
C) Activate osteoclast precursors and stimulate osteoclast activity
D) Stimulate calcitonin release

Answer: C) Activate osteoclast precursors and stimulate osteoclast activity

Question: Which of the following directly inhibits bone resorption?

A) Parathyroid Hormone
B) RANK Ligand
C) Osteoprotegerin
D) PTH-related Peptide

Answer: C) Osteoprotegerin

Question: The final, active form of Vitamin D is synthesized in which organ?

A) Skin
B) Liver
C) Kidney
D) Intestine

Answer: C) Kidney

Question: Which hormone's effects are more powerful in regulating plasma calcium than calcitonin?

A) Insulin
B) Glucagon
C) PTH and Vitamin D
D) Growth Hormone

Answer: C) PTH and Vitamin D

Question: Lithium therapy can cause hypercalcemia by:

A) Inhibiting PTH secretion
B) Mimicking PTH action on bone
C) Initiating an increase in calcium levels (mechanism not fully defined)
D) Destroying the parathyroid glands

Answer: C) Initiating an increase in calcium levels (mechanism not fully defined)

Question: Milk-alkali syndrome involves hypercalcemia due to:

A) Excessive PTH production
B) Increased intake of milk and absorbable antacids
C) Autoantibodies against the CaSR
D) Tumor lysis of bone

Answer: B) Increased intake of milk and absorbable antacids

Question: Acquired hypoparathyroidism is most commonly a result of:

A) Genetic disorders
B) Neck surgeries/thyroidectomy
C) Vitamin D deficiency
D) Autoimmune polyglandular syndrome

Answer: B) Neck surgeries/thyroidectomy

Question: Albright's Hereditary Osteodystrophy is associated with:

A) Primary Hyperparathyroidism
B) Pseudohypoparathyroidism
C) Medullary Thyroid Carcinoma
D) Hypervitaminosis D

Answer: B) Pseudohypoparathyroidism

Question: The "rachitic rosary" is a clinical feature of:

A) Osteoporosis
B) Osteomalacia
C) Rickets
D) Osteitis Fibrosa Cystica

Answer: C) Rickets

Question: Bone pain and loss of bone mass due to excessive resorption is a key feature of:

A) Hypoparathyroidism
B) Osteitis Fibrosa Cystica
C) Osteomalacia
D) Medullary Thyroid Carcinoma

Answer: B) Osteitis Fibrosa Cystica

Question: A reduction in bone strength and increased fracture risk due to porous bone describes:

A) Osteoporosis
B) Rickets
C) Osteomalacia
D) Paget's disease

Answer: A) Osteoporosis

Question: Which element is crucial for the mineralization of bone?

A) Sodium
B) Potassium
C) Calcium
D) Chloride

Answer: C) Calcium

Question: The process of osteoclastogenesis is:

A) The formation of bone by osteoblasts
B) The formation of activated osteoclasts
C) The apoptosis of osteocytes
D) The mineralization of osteoid

Answer: B) The formation of activated osteoclasts

Question: What is the primary source of PTH in the body?

A) Thyroid Gland
B) Parathyroid Glands
C) Mammary Glands
D) Kidneys

Answer: B) Parathyroid Glands

Question: Which cell type is targeted by PTH to initiate bone resorption?

A) Osteoclasts directly
B) Osteoblasts and osteocytes
C) Chondrocytes
D) Bone marrow stem cells

Answer: B) Osteoblasts and osteocytes

Question: The Calcium Stimulation Test for calcitonin uses which compound?

A) Pentagastrin
B) Calcium Gluconate
C) Potassium Chloride
D) Sodium Bicarbonate

Answer: B) Calcium Gluconate

Question: A peak calcitonin level of <10 ng/L after Pentagastrin stimulation is interpreted as:

A) Probable MTC
B) Possible MTC
C) Normal
D) C-cell Hyperplasia

Answer: C) Normal

Question: Procalcitonin is a precursor for which hormone?

A) Parathyroid Hormone
B) Calcitonin
C) Thyroxine
D) Vitamin D

Answer: B) Calcitonin

Question: Hypercalcemia of malignancy WITH bony metastases can be caused by all EXCEPT:

A) Direct tumor lysis
B) Osteoclast-activating factors
C) PTH-related peptide from distant tumors
D) Lymphokines with osteoclast-potentiating activity

Answer: C) PTH-related peptide from distant tumors

Question: The main hormonal regulator of intestinal calcium absorption is:

A) Parathyroid Hormone
B) Calcitonin
C) Vitamin D
D) PTH-related Peptide

Answer: C) Vitamin D

Question: Which condition results from the body producing autoantibodies against the parathyroid glands?

A) DiGeorge Syndrome
B) Familial Hypocalciuric Hypercalcemia
C) Hereditary Autoimmune Syndrome
D) Milk-alkali Syndrome

Answer: C) Hereditary Autoimmune Syndrome

Question: In PTH-ineffective hypoparathyroidism, the problem is:

A) The glands do not produce PTH.
B) The PTH produced is biologically inactive.
C) The target cells are resistant to PTH.
D) Vitamin D is deficient.

Answer: B) The PTH produced is biologically inactive.

Question: Bowing of the legs (genu varum) can be a deformity seen in:

A) Osteoporosis
B) Osteomalacia
C) Rickets
D) Osteitis Fibrosa Cystica

Answer: C) Rickets

Question: The primary reason calcitonin is not a major focus for calcium-related lab testing is:

A) It is too expensive to measure.
B) PTH and Vitamin D have more powerful regulatory roles.
C) It is only produced in disease states.
D) Its levels are too low to detect accurately.

Answer: B) PTH and Vitamin D have more powerful regulatory roles.

Question: Which hormone's action is summarized as "inhibits bone resorption, decreases blood calcium"?

A) Parathyroid Hormone
B) Vitamin D
C) Calcitonin
D) PTH-related Peptide

Answer: C) Calcitoni