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Hypercalcaemia. Calcium Metabolism. Intestine Bone kidney (2.1-2.6 mmol/l) 97% of reservoir in bone, chronic regulation. Kidney involved in minute to minute flux.Filters 8000mg daily. Net intestinal absorption is 200mg daily..

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calcium metabolism
Calcium Metabolism
  • Intestine Bone kidney (2.1-2.6 mmol/l)
  • 97% of reservoir in bone, chronic regulation.
  • Kidney involved in minute to minute flux.Filters 8000mg daily.
  • Net intestinal absorption is 200mg daily..
  • If long term calcium losses exceed net calcium absorption the deficit is resorbed from bone leading to demineralisation.
calcium metabolism pth
Calcium Metabolism - PTH
  • Parathyroid Hormone (PTH), 84 AA structure. Secreted from parathyroid gland in response to hypocalcemia.
  • Amino terminal (1-34 AA) contains the biological activity.
  • PTH acts on receptors in target tissues leading to stimulation of adenylaye cyclase activity.
effects of pth
Effects of PTH
  • Increases calcium reabsorption by the kidney.
  • Decreases phosphate reabsorption by the kidney.
  • Increases osteoclastic bone resorption.
calcium metabolism vitamin d
Calcium Metabolism- Vitamin D
  • Vitamin D formed in skin(D3 or cholecalciferol) by uv light. Major source of vitamin D (90%). Also present in diet. This is the inert form
  • Hydroxylated in the liver to 25-OH-VitD.
  • Renal hydroxylation to 1,25 dihydroxy vitamin D (very active metabolite). Renal also produces 24,25 dihydroxy vit D. (inactive)
  • Calcium deficiency leads to 1,25 Dit D production
  • 1,25 vit D acts on small intestine to increase calcium absorption.
  • Also acts on bone to cause resorption.
three forms of calcium in serum
Three forms of calcium in serum
  • Ionised (physiological form).
  • Protein-bound (50%), mainly to albumin
  • Complexed to citrate and phosphate(1-2%).
causes of hypercalcaemia
COMMON (97%) of all cases

Primary Hyperparathyroidism

Malignancy

LESS COMMON

Familial benign hypercalcaemia (FBH)

Sarcoidosis

Thyrotoxicosis

Vitamin D poisoning

Acute renal failure

Causes of Hypercalcaemia
causes of hypercalcemia rare
Causes of Hypercalcemia-RARE
  • Immobilisation
  • VIPomas
  • Tuberculosis
  • Milk-alkali syndrome
  • Addison’s Disease
  • Lithium
  • Thiazide diuretics
  • Parenteral feeding
symptoms
Symptoms
  • Tiredness and lethargy
  • Proximal muscle weakness
  • Polyuria, nocturia and thirst
  • Nausea Vomiting and constipation
  • Depression, psychosis and impaired consciousness.
signs
Signs
  • Proximal muscle weakness
  • Signs of Dehydration
  • Altered mental state.
primary hpt
Primary HPT
  • 500 cases/million
  • More common in females
  • Incidence increases with age
  • Autonomous production of PTH
  • Benign Adenoma
  • Asymptomatic pick-up.
hyperparathyroidism in other syndromes rare
Hyperparathyroidism in other syndromes (RARE)
  • MEN Type 1 (Parathyroid adenoma, Pituitary adenoma, and pancreatic islet cell tumours).
  • MEN Type 2 (Parathyroid adenoma, medullary thyroid carcinoma and phaeochromocytoma)
primary hpt diagnosis
Primary HPT - Diagnosis
  • Persistent Hypercalcaemia.
  • Low serum phosphate.
  • High normal or elevated PTH concentration.
  • 24h urinary Calcium excretion
  • Sestemebi scan
primary hpt treatment
Primary HPT- treatment
  • Parathyroidectomy.
  • Serum calcium should be normal within 24h.
  • Postoperative hypocalcaemia.
  • Recurrent laryngeal nerve injury.
familial benign hypercalcaemia fbh
Familial Benign Hypercalcaemia (FBH).
  • Familial, AD. Family history important.
  • Often come to light after failed parathyroidectomy
  • Benign. Asymptomatic.
  • Low urinary calcium excretion.
hypercalcaemia of malignancy
Hypercalcaemia of malignancy
  • Carcinomas of breast, lung, head and neck,renal.
  • Usually squamous carcinomas.
  • PTHrP increased
  • PTH normal
  • Low serum albumin, high ESR, anemia.
  • Myeloma, local bone resorption.
sarcoidosis
Sarcoidosis
  • Small numbers of patients with sarcoidosis develop hypercalcaemia.
  • May develop after prolonged sun exposure.
  • 1,25 diOH Vit D high, prodiced by alveolar macrophages. PTH is normal.
  • Corrected by Steroids
thyrotoxicosis
Thyrotoxicosis
  • Severe thyrotoxicosis
  • Increased calcium release from bone (Thyroxine acts on bone)
  • PTH is normal
  • Takes 4-6 weeks to resolve with antithyroid treatment
  • Persistent hypercalcaemia usually means concomitant HPT.