Calcium-Phosphate Pathology Flashcards
State some common causes of HYPERCALCAEMIA. (2)
- primary hyperparathyroidism
- malignancies (related to parathyroid gland)
State some common causes of HYPOCALCAEMIA. (3)
- thyroidectomy (decreased PTH)
- low VitD due to LOW INTAKE or LIVER/KIDNEY DISEASE
- high phosphate (binds to calcium to decrease ionised Ca2+ + increase FGF23 which inhibits VitD production)
State an example of a condition which causes SECONDARY HYPERPARATHYROIDISM.
Explain how this condition leads to hypercalcaema.
secondary hyperparathyroidism = conditions that result in compensatory overproduction of PTH –> CKD
- CKD –> vitamin D (1,25-DIHYDROXYCHOLECALCIFEROL) decreases as the final activation step occurs in kidneys
- Decreased vitamin D –> calcium reabsorption at DCT decreases + calcium absorption at gut decreases
- Decreased calcium + High phosphate –> stimulates compensatory increase in PTH
Recap: State the functions of calcium in the body (7)
- muscle contraction
- second messenger
- activation of enzymes
- blood coagulation
- nerve conduction
- myocardial function
- bone and teeth formation
State the effects of HYPOCALCAEMIA. (5)
- clostridium tetani (spastic paralysis)
- seizures
- heart failure, ECG changes
- poor dentition, hair, nails, hermatological aspects
- nervous system pathologies
What is the difference between OSTEOPOROSIS and OSTEOMALACIA
osteoporosis - resorption > formation (brittle bones)
osteomalacia - soft and weakened bones
State some causes of OSTEOPOROSIS (3)
- menopause (estrogen deficiency –> decreased apoptosis of osteoclasts which is mediated by estrogen –> increased resorption)
- cushing’s syndrome (hypercortisolism –> promote osteoclast, inhibit osteoblast)
- increased steroid intake
State some causes of OSTEOMALACIA (3)
- insufficient vitamin D (kidney/liver dysfunctions)
- hypophosphotaemia
- increased FGF23 activity –> decreased vitamin D –> decreased calcium and phosphate absorption and reabsorption
Recap: State the calcium states in plasma. State the percentage of each state in plasma.
- calcium bound to albumin (45%)
- ionised calcium (50%)
- complex with citrate, phosphate, bicarbonate (5%)
State the 3 factors that influence PTH secretion.
- ionised calcium ion concentration
- 1,25-DIHYDROXCHOLECALCIFEROL (vitamin D)
- magnesium (co-factor) (minor effects - only large increase in Mg2+ causes PTH production to fall)
Recap: State the actions of PTH.
Function - increase Ca2+, decrease PO42-
- stimulates osteoclast activity to increase bone resorption -> release calcium and phosphate from bone
- stimulate calcium reabsorption from DCT
- stimulate phosphate excretion from PCT
- promotes formation of 1,25-dihydroxycholecalciferol –> indirectly increases calcium absorption from gut
State the clinical features of HYPERCALCAEMIA. (8)
STONES, BONES, GROANS, MOANS, TIRED, OVERTONES, +2
- stones - nephrolithiasis
- bones - bone pain (promote activity of osteoclasts)
- groans - abdominal pain, n&v, constipation, PUD, acute pancreatitis, cholelithiasis
- moans - anxiety, depression
- tired - fatigue
- overtones - muscle weakness
- cardiac arrhythmias
- hypercalcaeia-induced diabetes insipidus
State some common conditions that cause HYPERCALCAEMIA (7)
- malignancies (multiple myeloma, humoral hypercalcaemia of malignancy (HMM))
- vitamin d excess (sarcoidosis, vitamin d intoxication)
- milk-alkali syndrome
- immobilisation
- familial hypocalciuric hypercalcaemia
- endocrine disorders (thyrotoxicosis, addison’s disease)
- drugs - thiazide diuretics
State the differences in HYPERPARATHYROIDISM and MALIGNANCY
After serum calcium levels >2.8mmol/L on more than 3 occasions
hyperparathyroidism - PTH undetectabole
malignancy - PTH detectable or high
State some common conditions related to PRIMARY HYPERPARATHYROIDISM(3).
- parathyroid adenoma
- parathyroid hyperplasia
- parathyroid carcinoma
Regarding PRIMARY HYPERPARATHYROIDISM, state
- biochemical features
- treatment
Regarding PRIMARY HYPERPARATHYROIDISM, state
- biochemical features - increased calcium, normal/decreased phosphate, metabolic acidosis
- treatment - treat underlying cause
State the biological markers of the MALIGNANT CAUSES OF HYPERCALACAEMIA
- Tumour with bony metastases release –> prostglandins, OAF (osteoclast activating factor)
- Multiple Myeloma –> OAF, cytokines, vitamin D
- Humoral Hypercalcaemia of Malignancy –> PTHrP (parathyroid hormone releasing protein) + accompanied by oat cell bronchial carcinoma, ovary, pancreas
State the investigation used for HYPERCALCAEMIA
measure PTH when serum adjusted calcium >2.8mmol/L on at least 3 occasions
- PTH undetectable - malignancy
- PTH detectable/high - primary hyperparathyroidism (adenoma, caricnoma, hyperplasia)
Regarding HYPOCALCAEMIA, state the
- clinical features
- treatment
HYPOCALCAEMIA
(1) Clinical features
- neurological - tetanus/fits
- cardiovascular - HF, MI
- cataracts
(2) Treatment
- oral calcium supplement
- vitamin d supplement
State the conditions that cause HYPOCALCAEMIA (5)
- hypoparathyroidism (parathyrodectomy, low Mg intake, idiopathic)
- vitamin d deficiency (malabsorption, diet, poor exposure to sun)
- renal/liver diseases (inability to produce vitamin d)
- pseudohypoparathyroidism
- rare causes (eg: acute pancreatitis)
State the test used to investigate HYPOCALCAEMIA
if serum adjusted calcium < 2.1mmol/L + exclude renal disease (urea and creatinine normal) –> MEASURE PTH LEVELS
- PTH low/undetectable –> post-parathyrodectomy/Mg deficient/idiopathic
- PTH high –> vitamin D deficient/pseudohypoparathyroidism
