Title: Magnesium accordion

Distribution

plasma distribution: (0.85 mmol/l)

- 55% ionic
- 30% protein bound
- 15% complexed

cellular distribution (0.8-1.2 mmol/l)

- 5-10% ionic
- 60% in mitochondria
- 25-30% bound

Sources

- Drinking water, especially when “hard” water
- Green leaves
- Vegetables, chocolate, fish, meat
- Dairy products have low magnesium content!

Intestinal Absorption

- small intestine and colon
- mostly paracellular (solvent drag)
- transcellular (active):
  - distal jejunum, ileum, colon
  - mechanism unknown
- 35-40% of dietary intake (normal intake), proportional to dietary intake
- reduced in diffuse intestinal disease, chronic laxative abuse

Renal Excretion

- ultrafiltration: 70% (ionic and complex)
- reabsorption
  - 15% prox. tubulus
  - 70% cortial thick ascending limb of Henle‘s loop
  - 10% distal convoluted tubulus

Homeostasis

- blood concentration regulated by gross influx and efflux via intestine, kidney, bone
- renal tubular reabsorption
- no strict hormonal regulation
- PTH has an effect on Mg homeostasis

Hypomagnesaemia

caused by:

- intestinal disorders (vomiting, diarrhea, malabsorption syndromes, pancreatitis)
- renal loss (excessive diuresis, hypercalcaemia, alcohol, drugs)
- endocrine and metabolic disorders (diabetes mellitus, hypercalcaemia, hyperparathyroidism, hungry bone syndrome)
- lactation
- wrong food preparation (long boiling in water)

symptoms: hyperexcitability, tetany, cardiac arrhythmia, hypocalcaemia because of disturbed PTH induced Ca-release from bone.

Hypermagnesaemia

caused by:

- high intake and renal failure

symptoms: neuromuscular disturbances, nausea, vomiting, cutaneous flushing, hypocalcaemia, hypotension, cardiac block -> cardiac arrest