Parathyroid

Prevalence is 1; 1000 total population and 1: 500 women more than 45 years
Most asymptomatic
Most detected on testing for other conditions

Primary hyperparathyroidism

Elevated PTH. Normal or increased serum Ca
Due to:
- Parathyroid adenoma (85%)
- Parathyroid hyperplasia (15%)
- Parathyroid carcinoma (<1%)

Picture provided by Fawzy Deghedy, Saudi German Hospital, Jeddah, Saudi Arabia

Secondary hyperparathyroidism

Elevated PTH. Low serum Ca
Due to chronic renal failure, malabsorption

Tertiary hyperparathyroidism

Elevated PTH following correction of cause of secondary hyperparathyroidism

Clinical Features of hyperparathyroidism

General Polydipsia, weight loss

Renal Colic, haematuria, back pain, polyuria

Cardiovascular Hypertension, heart block

Musculoskeletal Non-specific aches and pains, bone pain, pathological fractures

Gastrointestinal Anorexia, nausea, dyspepsia, constipation

Neurological Depression, lethargy, apathy, weakness, psychosis

Clinical presentations of hyperparathyroidism

Asymptomatic hypercalcaemia (50%)
Renal stones(28%)
Polyuria, polydipsia (5%)
Peptic ulcer (4%)
Hypertension(4%)
Bone disease(3%)
MEN 1 Syndrome(1%)

Biochemical investigation

Primary hyperparathyroidism
- Increased corrected calcium
- Increased PTH - mid region and C terminal assays most sensitive
- 75% hypercalciuria
- 50% hypophosphataemia
- Mild hyperchloraemic acidosis
Familial hypocalciuric hypercalcaemia
- Autosomal dominant with high penetrance
- <1% cases of hypercalcaemia
- Due to increased renal tubule absorption of calcium
- Urine Ca < 2.5 nmol/day
- serum PTH normal
- Benign condition - Parathyroid surgery not required
- Suspect if hypercalcaemia in several generations of a family
- Especially if member has had unsuccessful parathyroid surgery
- Normocalcaemic hypercalciuria
- Due to increased absorption of Ca from gut or primary renal tubular leak
- No benefit form parathyroid surgery

Preoperative parathyroid localisation

" The only preoperative localisation necessary is to choose an experienced surgeon" - Fuller Albright 1948

Opinion divided on preoperative localisation for primary surgery
Some will undertake primary surgery without investigation

Ultrasound

Operator dependent with variable accuracy
Will not usually detect normal parathyroids
Sensitivity up to 85% for abnormal glands
Able to identify intra-thyroid parathyroid glands
May miss deep or intra-thoracic glands

Computed tomography

Equally as accurate as ultrasound
Useful for identifying ectopic glands

Magnetic resonance imaging

Role still being defined. Potentially most useful
T₂ sequences weighted images produce best resolution between adenoma and normal tissue
Improve resolution with neck surface coils
85% lesions less than 0.5 cm detected

Scintigraphy

Combined ⁹⁹Tch (pertechnate) and ²⁰¹Th (thallium chloride) subtraction technique
Thyroid gland take up ⁹⁹Tch and ²⁰¹Th
Parathyroids take up ²⁰¹Th
Images subtracted leaving only parathyroid image
Best single preoperative localisation technique
Localises 85% of abnormal glands
Specificity adversely affected by ²⁰¹Th uptake in thyroid abnormalities
e.g. multinodular goitres, thyroid adenomas

Preoperative methylene blue

3.5 mg/kg body weight dissolved in 500 ml dextrose
Infused over 1 hour preoperatively
Selectively stains parathyroid glands
Normal glands stain pale green
Pathological glands stain dark blue or black

Selective venous catheterisation

Invasive procedure. Multiple samples from neck and mediastinal sites
PTH x2 than peripheral venous sample considered significant
Lateralising rather than localising procedure
Adenoma - unilateral elevation
Hyperplasia - bilateral elevation
Most use prior to re-exploration for recurrent disease

Surgical management of hyperparathyroidism

Indications for surgery

Significant symptoms
Corrected Ca more than 2.8 mmol/l
Complications of hypercalcaemia
? treatment of mild elevation or asymptomatic patients

Operative procedure

Experienced parathyroid surgeon
? normal gland ? Hyperplasia ? Adenoma
Frozen section may be useful
If adenoma and one normal gland - No further action
If hyperplasia - Remove all 4 glands and transplant one into marked forearm site

Persistent or recurrent hyperparathyroidism

Persistent hyperparathyroidism
- Hypercalcaemia within 6 months of initial surgery
- Usually due to missed adenoma
Recurrent hyperparathyroidism
- Hypercalcaemia more than 6 months after initial surgery
- Intervening period of normocalcaemia
- Usually inadequate surgery for hyperplasia
- Consider MEN syndromes
Review histology and recheck serum Ca
Offer surgery if Ca more than 3 mmol/l
Preoperative localisation essential
Recurrent parathyroid surgery has a higher morbidity and greater chance of failure

Bibliography

Bilezikian J P, Silverberg J S. Asymptomatic primary hyperparathyroidism. N Engl J Med 2004; 350: 1746-1751.

Davies M, Thomas P. Decision making in surgery: the surgical management of a raised serum calcium. Br J Hosp Med 1995; 53: 330 - 333.

Dijkstra B, Healy C, Kelly L M, McDermott E W, Hill A D K, O'Higgins N O. Parathyroid localisation - current practice. J R Coll Surg Ed 2002; 47: 599-607.

Goode A W. Parathyroid surgery. In: Johnson C D, Taylor I eds. Recent advances in surgery 18. Churchill Livingstone, Edinburgh 1995; 99-116.

Pattou F, Huglo D, Proye C. Radionuclide scanning in parathyroid diseases. Br J Surg 1998; 85: 1605-1616.

Wheeler M H. Primary hyperparathyroidism: a surgical perspective. Ann R Coll Surg Eng 1998; 80: 305-312.

Wijesinghe L. Leveson S H. Update on primary hyperparathyroidism. Hospital Update July 1996. 294 -298.

Hyperparathyroidism