Chemical Pathology - Calcium Flashcards
(47 cards)
Where is 99% of calcium found?
Stored in the skeleton (calcium reservoir)
What is the breakdown of free calcium in the body?
- 45% = ionised (free, biologically active form)
- 50% bound to albumin (affected by albumin level, therefore need to use corrected calcium)
- 5% bound to globulins + other ions
What are the two hormones involved in calcium metabolism?
- Parathyroid hormone (PTH)
- Calcitriol
What does Parathyroid do in relation to calcium?
Increases calcium in the blood
- Increases tubular 1α hydoxylation of Vitamin D (25(OH)D)
- Mobilises calcium from bone through osteoclast activation
- Increases renal calcium reabsorption
- Increases renal phosphate excretion
What does calcitriol (1,25(OH)2D) do in relation to calcium?
Increases calcium in the blood
- Increases calcium and phosphate absorption from the gut
- Bone remodelling
What hormone decreases calcium levels in the blood?
Calcitonin
What is the metabolism of Vitamin D?
- 7-dehydrocholesterol converts to cholecalciferol via sunlight
- Cholecalciferol is found in Vitamin D3 tablets + Fish oils
- Cholecalciferol is converted to calciferol (25-OH D3) by 25-hydroxylase in the liver
- Calciferol gets converted to Calcitriol (1,25(OH)2D) via 1α hydroxylase
What is the process of calcium control in the body?
- Decreased calcium causes PTH release from PTH gland
- Bone resorption occurs in osteoclsts from calcium stored in bone (Increases Ca in blood - PO4 increases)
- Ca reuptake in the kidney is increased (PO4 decreased) - Ca also excreted in urine
- PTH triggers 1α dehydroxylase activity, converting calciferol to calcitriol
- Calcitriol worse in the gut to increase Ca + PO4 uptake
Which conditions have the highest to lowest calcium concentrations?
(Primary Hyperparathyroidism, Secondary Hyperparathyroidism, Parathyroud Carcinoma, Osteomalacia, Osteoporosis)
- Parathyroid Carcinoma
- Primary Hyperparathyroidism
- Osteoporosis
- Secondary Hyperparathyroidism
- Osteomalacia
What is the defect in primary hyperparathyroidism?
Intrinsic problem with parathyroid gland, causing increased PTH
What are the blood results of primary hyperparathyroidism?
(Ca, PO4, PTH, ALP, Vit D)
- Ca: Increased
- PO4: Decreased
- PTH: Increased/Normal
- ALP: Increased/Normal
- Vit D: Normal
What is the defect in secondary hyperparathyroidism?
Pathology outside parathyroid gland: stimulation of parathyroid gland to produce more PTH
What are the blood results of secondary hyperparathyroidism?
(Ca, PO4, PTH, ALP, Vit D)
- Ca: Decreased
- PO4: Increased
- PTH: Increased
- ALP: Increased
- Vit D: Decreased/Normal
What is the defect in tertiary hyperparathyroidism?
Autonomous PTH secretion
What are the blood results of tertiary hyperparathyroidism?
(Ca, PO4, PTH, ALP, Vit D)
- Ca: Increased/Normal
- PO4: Decreased/Increased
- PTH: Increased
- ALP: Increased/Normal
- Vit D: Decreased/Normal
What is the defect in hypoparathyroidism?
Low levels of PTH
What are the blood results of hypoparathyroidism?
(Ca, PO4, PTH, ALP, Vit D)
- Ca: Decreased
- PO4: Increased
- PTH: Decreased
- ALP: Decreased/Normal
- Vit D: Normal
What is the defect in Rickets/osteomalacia?
Vitamin D deficiency
What are the blood results of rickets/osteomalacia?
(Ca, PO4, PTH, ALP, Vit D)
- Ca: Decreased
- PO4: Decreased
- PTH: Increased
- ALP: Increased
- Vit D: Decreased
What is the defect in Paget’s disease?
Re-modelling of bone
What are the blood results of Paget’s disease?
(Ca, PO4, PTH, ALP, Vit D)
- Ca: Normal
- PO4: Normal
- PTH: Normal
- ALP: Increased
- Vit D: Normal
What is the defect in osteoporosis?
Bone loss
What are the blood results of osteoporosis?
(Ca, PO4, PTH, ALP, Vit D)
- Ca: Normal
- PO4: Normal
- PTH: Normal
- ALP: Normal
- Vit D: Normal
What are some causes (and their prevalence) of primary hyperparathyroidism?
- Single parathyroid adenoma (80%)
- Hyperplasia + multple adenomas (15%)
- Carcinomas (mostly non-functional) (0.5%)
- MEN1 (adenoma) + MEN2 (hyperplasia)
