Hyperparathrydoism Flashcards
Define
Parathyroid hormone (PTH) is normally secreted in response to low ionized Ca2+ levels, by 4 parathyroid glands situated posterior to the thyroid
PTH acts by:
• ↑Osteoclast activity releasing Ca2+ and PO43– from bones • ↑Ca2+ and ↓PO43− reabsorption in the kidney
• ↑Active 1,25 dihydroxy-vitamin D3 production
Overall effect is ↑Ca2+ and ↓PO43−
Primary hyperparathyroidism
↑PTH unrelated to the plasma Ca2+ concentration
80% solitary adenoma
20% hyperplasia o all glands <0.55 parathyroid cancer
Secondary hyperparathyroidism
↑PTH secondary to hypocalcaemia
↓Ca2+, ↑PTH (appropriately)
Causes: decreased vitamin D intake, chronic renal failure Symptoms: of hypocalcaemia
Tertiary hyperparathyroidism
Autonomous PTH secretion following chronic 2ndary hyperparathyroidism
↑Ca2+, ↑↑ PTH (inappropriately)
Occurs after prolonged secondary hyperparathyroidism
Causing glands to act autonomously having undergone hyperplastic or adenomatous change
This causes ↑Ca2+ from ↑↑secretion of PTH unlimited by feedback control
Malignant hyperparathyroidism
Parathyroid-related protein (PTHrP) is produced by some squamous cell lung cancers, breast and renal cell carcinomas
This mimics PTH resulting in ↑Ca2+
Epidemiology
Primary - incidence of 5/100,000
Twice as common in FEMALES
Peak incidence: 40-60 yrs
Causes
Primary
- Parathyroid adenoma
- Parathyroid hyperplasia
- Parathyroid carcinoma
- MEN syndrome
Secondary
- Chronic renal failure
- Vitamin D deficiency
Symptoms of primary
↑Ca2+: weak, tired, depressed, polydipsia, dehydrated (but polyuric), renal stones, abdominal pain, pancreatitis, ulcers, constipation
Bone resorption effects: pain, fractures, osteopenia/osteoporosis
↑BP
↑Ca2+, ↑PTH (or inappropriately normal)
↑Alk Phos from bone activity
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Primary - many patients have mild hypercalcaemia and may be asymptomatic
Symptoms/Signs of hyperclacaemia:
- Polyuria
- Polydipsia
- Renal calculi
- Bone pain
- Abdominal pain
- Nausea
- Constipation
- Psychological depression
- Lethargy
Secondary - may present with signs/symptoms of HYPOcalcaemia or of the underlying cause (e.g. renal failure, vitamin D deficiency)
Investigations
- U&Es
- Serum calcium (high in primary and tertiary, low/normal in secondary)
- Serum phosphate (low in primary and tertiary, high in secondary)
- Albumin
- ALP
- Vitamin D
- PTH
Primary Hyperparathyroidism
- Hyperchloraemic acidosis
- Normal anion gap
- Due to PTH inhibition of renal reabsorption of bicarbonate
- Urine - high PTH in the presence of high calcium can also be caused by familial hypocalciuric hypercalcaemia (FHH)
- Calcium: creatinine clearance ratio can help differentiate between primary hyperparathyroidism and FHH
- Renal ultrasound - can visualise renal calculi
Management
Acute Hypercalcaemia
- IV fluids
- Avoid factors that exacerbate hypercalcaemia (e.g. thiazide diuretics)
- Maintain adequate hydration
- Moderate calcium and vitamin D intake
Surgical Management
- Subtotal parathyroidectomy
- Total parathyroidectomy
Secondary Hyperparathyroidism Management
- Treat underlying cause (e.g. renal failure)
- Calcium and vitamin D supplements may be needed
Complications
Primary
- Increased bone resorption
- Increased tubular calcium reabsorption
- Increased 1a-hydroxylation of vitamin D
- All of these lead to hypercalcaemia
Secondary
- Increased stimulation of osteoclasts and increased bone turnover
- This leads to osteitis fibrosa cystica
Complications of surgery
- Hypocalcaemia
- Recurrent laryngeal nerve palsy
Prognosis
Primary - surgery is curative for benign disease in most cases
Secondary or Tertiary - same prognosis as chronic renal failure
