Disorders of Calcium and Phosphate Metabolism

Question 1

Hypercalcaemia:
What can it be caused by?

What conditions cause an ↑PTH and ↓PTH?

What are the symptoms?

What ECG changes are seen with it?

What investigations are done?

How is it treated?

What is Hypercalcaemia of Malignancy?

Answer 1

• ↑PTH or ↓PTH
• ↑PTH; Hyperparathyroidism, Cancer
  ↓PTH; Cancer, Hypervitaminosis D (Granulomatous diseases, Exogenous sources), Increased Bone Turnover (Acromegaly, Thyrotoxicosis)
• Confusion, Fatigue, Depression, Coma, Polyuria, Renal stone, Nephrogenic DI, Muscle weakness, Osteoporosis, Bradycardia, Hypertension, Constipation, Pancreatitis, Band Keratopathy (Ca deposits between sclera and iris)
• SHORTENED QT INTERVAL
• U&E Magnesium, Calcium, Phosphate, Vitamin D, PTH, Chest X-ray, ACE, Myeloma screen
• • Surgery
  • Saline Rehydration; ↑↑↑Ca is Nephrotoxic
  • Frusemide; Loop diuretic to ↑Ca excretion
  • Pamidronate; ↓Bone resorption
  • Calcitonin; works to ↓[Ca]
  • Prednisolone - ↓Calcitriol (Vit D) production
  • Dialysis
• • Metastatic Solid Tumours; Lung, Breast, Kidney, Prostate
  • Small Cell Lung Cancer
  • Osteoclast-activating factor; Lymphoma, Multiple myeloma

Question 2

Hyperparathyroidism:
What is Primary hyperparathyroidism?
→ What’s it due to?

What is Secondary hyperparathyroidism?
→ Why does it occur?
→ What’s it due to?

What is Tertiary hyperparathyroidism?
→ When does it occur?

Answer 2

• ↑PTH production = ↑Ca2+;
  → Single Adenoma or Diffuse Hyperplasia, Rarely due to a Parathyroid Carcinoma
• ↓Ca2+ causing ↑PTH production;
  → Compensatory hyperfunctioning of the Parathyroid gland caused by Hypocalcaemia or Peripheral resistance to PTH
  → Chronic renal insufficiency, Calcium malabsorption, ↓Vitamin D, Poor Vitamin D metabolism
• ↑Ca2+ and ↑PTH;
  → Following previous Secondary Hyperparathyroidism when Glandular over-function occurs despite correction of underlying abnormality e.g. Renal transplantation

Question 3

Hypocalcaemia:
What can it be caused by?

What conditions cause an ↑PTH and ↓PTH?

What does it lead to?

What are the symptoms?

What ECG changes are seen with it?

How is it treated?

Answer 3

• ↑PTH or ↓PTH
• ↑PTH/Vitamin D deficiency - Renal/Liver disease, Poor dietary Calcium, Malabsorption, Chelation after a blood transfusion secondary to Pancreatitis, Rhabdomyolysis, Chemotherapy
  ↓PTH - Pseudo-Hypoparathyroidism, Mutation of Ca receptor
• Osteomalacia/Rickets
• Muscle spasms, Paresthesia (pins + needles), Chvostek and Trousseau signs, Confusion, Seizures
• PROLONGED QT INTERVAL
• Treat underlying causes (correct other electrolyte disorders and discontinue offending drugs), Oral calcium supplementation, IV Calcium Gluconate, Vitamin D supplementation

Question 4

Hypoparathyroidism:
What is Primary hypoparathyroidism?

What is Secondary hypoparathyroidism?

Pseudo-hypoparathyroidism:
What is it?

What are the symptoms?

Answer 4

• Congenital or Autoimmune
• Post neck surgery or Radioiodine therapy
  o Hypomagnesemia, Hypermagnesemia - impaired PTH production
• Post receptor defect of PTH receptor; ↓Ca, ↓Vit D Hydroxylation, ↑Phosphate, ↑PTH
• Short stature, Obesity, Round face, ↓IQ, Brachydactyly (shortened digits), Ectopic Calcification (e.g. brain, heart)