Summary

Primary Hyperparathyroidism (PHPT) is a disorder of inappropriate parathyroid hormone (PTH) hypersecretion, resulting in hypercalcaemia and hypophosphataemia. It is the most common cause of hypercalcaemia in the outpatient setting. The condition is usually caused by a solitary parathyroid adenoma (80-85%). While the classic presentation involves "bones, stones, abdominal groans, and psychic moans," most modern patients are asymptomatic ("biochemical PHPT") diagnosed incidentally. Definitive management is surgical parathyroidectomy, indicated for all symptomatic patients and asymptomatic patients meeting specific criteria (age less than 50, renal/bone involvement). [1,2]

Key Facts

• Incidence: 1-7 per 1,000 adults; peak incidence in post-menopausal women (50-60 years).
• Cause: Solitary adenoma (85%), Multi-gland hyperplasia (15%), Carcinoma (less than 1%).
• Biochemistry: Hypercalcaemia + Elevated (or inappropriately normal) PTH + Low Phosphate.
• Diagnosis exclusion: Familial Hypocalciuric Hypercalcaemia (FHH) must be excluded before surgery.
• Treatment: Surgery is the unique curative therapy (cure rate >95%).
• Surgical Localisation: Sestamibi scan (nuclear medicine) and Ultrasound are standard.

Clinical Pearls

Inappropriately Normal PTH: A patient with hypercalcaemia should have a SUPPRESSED PTH (e.g., less than 1.0 pmol/L). If calcium is high (2.8 mmol/L) and PTH is "normal" (e.g., 4.5 pmol/L, within range 1.6-6.9), this is Primary Hyperparathyroidism. The PTH is inappropriate for the calcium level.

Exclude FHH: Before referring for surgery, check the 24-hour urinary calcium. Familial Hypocalciuric Hypercalcaemia (FHH) mimics PHPT but is benign effectively and surgery does not help. Low urine calcium (Ca/Cr clearance less than 0.01) suggests FHH.

Hungry Bone Syndrome: After removing a parathyroid adenoma in a patient with severe bone disease, the "starved" bones rapidly uptake calcium, causing severe, prolonged Post-Op Hypocalcaemia. Watch for tingling and tetany.

Normocalcaemic PHPT: A variant where calcium is normal but PTH is consistently high (after excluding vitamin D deficiency and CKD). These patients may progress to classic PHPT.

General

• Dehydration signs.
• Confusion (if severe).

Neck

• Inspection: Thyrotoxicosis scar?
• Palpation: Usually NORMAL. A typical adenoma (1-2cm, 1g) is too soft/deep to feel.
  • If you feel a mass: Thyroid nodule? Parathyroid Carcinoma?
• Vocal Cords: Check voice (hoarseness).

Skeletal

• Vertebral tenderness (fractures).
• Proximal myopathy testing.

Cure Rates

• Surgery: >95-98% permanent cure.
• Recurrence: Rare in sporadic adenoma. Higher in MEN1 or Carcinoma.

Long-term Benefits

• Bone density improves significantly (10-15% increase in first year).
• Fracture risk returns to normal.
• Stone formation risk drops.
• Neurocognitive symptoms may improve (variable).
• Cardiovascular mortality risk reduces.

Key Guidelines

Landmark Studies

1. Silverberg et al (1999) - Natural History

• Question: Surgery vs Observation in asymptomatic PHPT?
• Result: Surgery improved bone density. Observation group stable for years but some progressed.
• Impact: Justified observation in correctly selected patients.

2. Fourth International Workshop (2014) Criteria for Surgery Surgery recommended if ANY met:

1. Serum Ca >0.25 mmol/L (>1mg/dL) above upper limit.
2. Skeletal: T-score less than -2.5 (Lumbar, Hip, or Radius) or Vertebral Fracture.
3. Renal: eGFR less than 60 ml/min.
4. Renal: Stones or Nephrocalcinosis on imaging, or High Urine Ca risk.
5. Age less than 50 years.

What is Primary Hyperparathyroidism?

You have four tiny glands in your neck (behind the thyroid) called parathyroid glands. Their job is to control calcium levels. In this condition, one of these glands has grown a benign lump (adenoma) and is working overtime, putting too much hormone into your blood.

What does the hormone do?

It takes calcium OUT of your bones and puts it into your blood. This causes two problems:

1. High Blood Calcium: Can make you feel tired, thirsty, confused, or cause kidney stones.
2. Weak Bones: Because the calcium is being stripped out, your bones become thinner (osteoporosis).

Why do I have it?

It is usually just "bad luck" - a single cell grew into a benign lump. It is rarely cancerous (less than 1%). It is more common in women after menopause.

How is it treated?

• Surgery: This is the only cure. A surgeon removes the one overactive gland (or glands) through a small cut in the neck. It takes about 45 minutes and has a very high success rate.
• Monitoring: If your calcium is only slightly high and your bones/kidneys are healthy, we might just watch it with yearly blood tests and bone scans.

Common Exam Questions

1. MRCP/USMLE: "A 55-year-old woman has Calcium 2.85, Phos 0.6, PTH 6.5 (Normal 1.6-6.9). Diagnosis?"
   • Answer: Primary Hyperparathyroidism. (PTH is inappropriately normal for the high calcium).
2. Surgical: "What are the indications for surgery in asymptomatic PHPT?"
   • Answer: Age less than 50, Ca >0.25 above limit, Osteoporosis (less than -2.5), Renal impairment (less than 60), Stones.
3. Pathology: "Distinguish PHPT from FHH."
   • Answer: Urine Calcium. Low in FHH, Normal/High in PHPT.
4. Radiology: "What is the classic X-ray finding in severe disease?"
   • Answer: Subperiosteal resorption (radial aspect of middle phalanges) or Pepper-pot skull.

Viva Points

• Sestamibi: Sestamibi concentrates in mitochondria-rich tissue (adenoma/heart). Washout is slower in parathyroid than thyroid.
• Intraop PTH: Miami criteria: >50% drop from baseline 10 mins after excision = Cure.
• MEN Syndromes: Always consider MEN1 (3Ps) in young patients (less than 30).

Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.