Y1S2 008 I Biochem Regulation of Calcium Levels by Hormones

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What is the primary function of Parathyroid Hormone (PTH)?

Regulating thyroid hormone production

Maintaining plasma [Ca2+] levels (correct)

Regulating inorganic phosphate concentration

Controlling extracellular fluid pH

How many amino acids are present in the intact Parathyroid Hormone (PTH)?

84 (correct)

150

115

90

What is the approximate half-life of intact Parathyroid Hormone (PTH) in the blood?

10-12 minutes

5-6 minutes

1-2 minutes

3-4 minutes (correct)

What is the approximate total weight of parathyroid tissue in the body?

150 mg Signup and view all the answers

What is the role of Calcitonin in regulating calcium concentration in the extracellular fluid?

Minor role Signup and view all the answers

How many parathyroid glands are usually found in the human body?

4 Signup and view all the answers

What is the primary effect of PTH on osteoclasts?

Stimulation of osteoclast development Signup and view all the answers

What is the active metabolite of vitamin D3?

1,25-DHCC Signup and view all the answers

Where is the 1α-hydroxylase enzyme located?

Proximal convoluted tubules of the nephrons Signup and view all the answers

What is the effect of PTH on plasma calcium levels?

Increase in plasma calcium levels Signup and view all the answers

What is the precursor of cholecalciferol?

7-hydrocholesterol Signup and view all the answers

What is the net result of PTH actions on bone?

Increase in bone resorption Signup and view all the answers

What directly stimulates the activity of 1α-hydroxylase?

PTH and hypophosphataemia Signup and view all the answers

What is the role of calbindin-D in the intestinal mucosa?

Promotes the absorption of calcium and phosphate Signup and view all the answers

What is the effect of calcitriol on bone mobilization?

Stimulates bone resorption Signup and view all the answers

What is the function of osteocalcin in bone formation?

Is a marker of bone formation and turnover Signup and view all the answers

What is the role of alkaline phosphatase in bone formation?

Is involved in the formation of new bone Signup and view all the answers

What is the effect of 1:25-DHCC on 25-HCC?

Stimulates its hydroxylation Signup and view all the answers

What is the effect of calcitonin on osteoclast activity?

It inhibits osteoclast activity Signup and view all the answers

What is the primary target cell for calcitonin?

Osteoclast Signup and view all the answers

What is the effect of calcitonin on renal reabsorption of calcium and phosphate?

It reduces renal reabsorption of calcium and phosphate Signup and view all the answers

During which periods is plasma calcitonin elevated?

During pregnancy and lactation Signup and view all the answers

What is the mechanism by which calcitonin acts on its target cells?

Via increased cAMP concentrations Signup and view all the answers

What is the effect of calcitonin on osteoblastic activity?

It increases osteoblastic activity Signup and view all the answers

What is the most common single presenting complaint of Primary Hyperparathyroidism?

Renal stones Signup and view all the answers

What is the primary cause of Hypercalcemia in Primary Hyperparathyroidism?

Combined effects of PTH-induced bone resorption, intestinal calcium absorption, and renal tubular reabsorption Signup and view all the answers

What is the most serious complication of Primary Hyperparathyroidism?

Deposition of calcium in the kidney tubules Signup and view all the answers

What is the underlying cause of Secondary Hyperparathyroidism?

Hypocalcemia and associated hypertrophy of the glands Signup and view all the answers

What is the result of the reduction of renal production of 1,25-dihydroxycholecalciferol (1,25-DHCC)?

Hyperphosphaturia Signup and view all the answers

What is the characteristic of the disorder in Primary Hyperparathyroidism?

Hypercalcemia, hypophosphatemia, and hyperphosphaturia Signup and view all the answers