Makindo Medical Notes

Related Subjects: |PTH Physiology |Calcium Physiology |Magnesium Physiology |Calcitonin |Hypocalcaemia |Hypercalcaemia |Hypomagnesaemia |Hypermagnesaemia |Primary Hyperparathyroidism |Familial hypocalciuric hypercalcaemia (FHH) |Sarcoidosis

Watch for hypocalcemia after surgery to ensure calcium levels return to normal and do not drop too low.

About

• An albumin-adjusted serum calcium level above 2.6 mmol/L (UK standard).
• A common cause of mild, asymptomatic hypercalcemia.
• Approximately 10% are associated with Autosomal Dominant MEN I and II.
• Predominantly affects females over males, with a prevalence of 1 in 300.

Physiology

• Typically, individuals have four parathyroid glands located posteriorly to the thyroid gland.
• Secretes parathyroid hormone (PTH) in response to low calcium levels, which helps regulate calcium and phosphate in the body.
• PTH acts by enhancing the synthesis of active vitamin D, facilitating calcium absorption and increasing calcium release from bones.

Aetiology

• Single adenoma: 85% of cases.
• Multiple adenomas: Often seen in MEN1 syndrome.
• Diffuse hyperplasia: Involvement of all glands.
• Parathyroid carcinoma: Less than 1% of cases.

Clinical Effects of Chronic Hypercalcemia

• May be asymptomatic for extended periods.
• Bone: Pain, weakness, osteoporosis, and increased risk of fractures.
• Kidneys: Renal stones, polyuria, nephrogenic diabetes insipidus, renal tubular acidosis.
• Mental health: Depression, mood swings, and psychiatric manifestations.
• Gastrointestinal: Constipation, pancreatitis, peptic ulcer disease.
• Cardiac: Hypertension, arrhythmias.

Differential Diagnosis

• Malignant hypercalcemia: Elevated PTH-related protein (PTHrp), high/normal urinary calcium; exclude myeloma.
• Familial hypocalciuric hypercalcemia (FHH): Autosomal dominant, low urinary calcium, normal/high PTH.
• Drug-induced: Lithium or thiazides may raise calcium; consider stopping and reassessing.

Investigations

• Blood tests: Elevated serum calcium, possible low phosphate, raised/normal alkaline phosphatase.
• PTH levels: Inappropriately raised with high calcium.
• X-rays: May show osteitis fibrosa cystica with bone resorption.
• Urinary calcium: Raised in around 30% of cases.
• DEXA scan: Used to assess bone density and osteopenia.
• Imaging for adenoma localization: Ultrasound of the neck, sestamibi scintigraphy with CT, or venous sampling.

Management

• Conservative: Hydration, cessation of calcium-raising drugs, and monitoring.
• Surgery: Parathyroidectomy is recommended for symptomatic patients or those with skeletal/renal complications.
• Three and a half glands removed in cases of diffuse hyperplasia.
• Postoperative monitoring for hypocalcemia.
• Non-surgical candidates: Monitor serum calcium, PTH, bone density every 1-2 years; consider bisphosphonates or cinacalcet for medical management.

Surgical Indications

• Serum calcium > 0.25 mmol/L above normal.
• Urinary calcium excretion > 10 mmol/24hr.
• Creatinine clearance < 30% below normal.
• Bone density T-score < -2.5.
• Patient request due to symptoms or lifestyle impact.

Postoperative Complications

• Hypocalcemia: “Hungry bone syndrome,” often transient; managed with calcium/vitamin D supplements if needed.
• Recurrent laryngeal nerve injury: Possible hoarseness or voice changes.
• Bleeding: Rare but may cause airway compromise; immediate intervention required.

References

• Pathophysiology of Primary Hyperparathyroidism
• Calcium Regulation