What are the symptoms and treatment options for an elderly female with hyperparathyroidism (Primary Hyperparathyroidism), elevated Parathyroid Hormone (PTH) levels, and mild hypocalcemia (low calcium levels)?

Management of Elevated PTH (175 pg/mL) with Normal Calcium (9.7 mg/dL) in an Elderly Female

This presentation most likely represents secondary hyperparathyroidism due to vitamin D deficiency or inadequate calcium intake, and the first-line approach is to check 25-OH vitamin D levels and ensure adequate vitamin D repletion (targeting >20 ng/mL) along with adequate dietary calcium intake before considering other diagnoses. 1

Understanding the Clinical Picture

The combination of elevated PTH with normal calcium is not primary hyperparathyroidism, which requires hypercalcemia or high-normal calcium with elevated PTH 2, 3. This biochemical pattern indicates the parathyroid glands are responding appropriately to a stimulus—most commonly vitamin D deficiency or calcium deprivation 1.

Potential Symptoms

While this patient may be asymptomatic, secondary hyperparathyroidism can cause:

• Musculoskeletal symptoms: Bone pain, muscle weakness, and myalgias due to increased bone resorption and calcium mobilization 4
• Fatigue and generalized weakness: Common non-specific symptoms associated with vitamin D deficiency and secondary hyperparathyroidism 5
• Osteopenia or osteoporosis: Chronic elevation of PTH increases bone turnover and can lead to decreased bone density 4, 3
• Fracture risk: Long-standing secondary hyperparathyroidism increases pathologic fracture risk through accelerated bone resorption 4

Important caveat: Many patients with this biochemical pattern are completely asymptomatic, discovered incidentally on routine laboratory testing 3.

Diagnostic Workup

Before initiating treatment, complete the following evaluation:

• Measure 25-OH vitamin D levels: This is the single most important test, as vitamin D deficiency is the most common cause of this presentation and must be ruled out 1, 6
• Assess dietary calcium intake: Detailed dietary history to determine if calcium intake meets age-appropriate recommendations (adults: 950-1200 mg/day) 1, 6
• Check renal function: Measure serum creatinine and eGFR, as chronic kidney disease is a major cause of secondary hyperparathyroidism 1, 6
• Measure serum phosphorus: Helps differentiate between various causes of secondary hyperparathyroidism 1

Treatment Algorithm

Step 1: Vitamin D Repletion (First-Line)

• Supplement with cholecalciferol or ergocalciferol if 25-OH vitamin D is below 20 ng/mL (50 nmol/L), which is the most common scenario 1, 6
• Target vitamin D levels >20 ng/mL to allow proper PTH regulation 1
• Typical dosing: 1000-2000 IU daily for maintenance, or higher loading doses (50,000 IU weekly) for severe deficiency 1

Step 2: Ensure Adequate Calcium Intake

• Verify dietary calcium intake meets recommendations: 950-1200 mg/day for adults 1, 6
• Add calcium supplementation (calcium carbonate or citrate) if dietary intake is insufficient 1
• Calcium should be taken with food to optimize absorption 1

Step 3: Reassess After Repletion

• Recheck PTH, calcium, and vitamin D levels after 3 months of adequate supplementation 1
• If PTH normalizes, continue maintenance vitamin D and calcium 1
• If PTH remains elevated despite adequate vitamin D (>20 ng/mL) and calcium intake, consider other causes including early CKD or malabsorption 1, 6

Special Considerations for CKD Patients

If renal function is impaired (eGFR <60 mL/min/1.73 m²):

• Active vitamin D sterols (calcitriol, alfacalcidol) may be needed instead of native vitamin D, as the kidney's ability to convert 25-OH vitamin D to active 1,25-dihydroxyvitamin D is impaired 1, 6
• Target PTH levels of 150-300 pg/mL for dialysis patients, though this patient is not on dialysis 1
• Monitor calcium and phosphorus closely when using active vitamin D to avoid hypercalcemia 1, 6

Critical Pitfalls to Avoid

• Do not assume primary hyperparathyroidism: With normal calcium, this is secondary hyperparathyroidism until proven otherwise 1, 2
• Do not skip vitamin D assessment: Failing to check vitamin D status is the most common diagnostic error and can lead to inappropriate workup or treatment 1
• Do not use cinacalcet in this setting: Cinacalcet is contraindicated when calcium is not elevated and is only indicated for hypercalcemia in primary hyperparathyroidism or parathyroid carcinoma, or for secondary hyperparathyroidism in dialysis patients 7
• Do not order parathyroid imaging: Imaging is not indicated without confirmed primary hyperparathyroidism (hypercalcemia + elevated PTH) 2, 3

When to Consider Alternative Diagnoses

If PTH remains elevated after 3-6 months of adequate vitamin D repletion (>20 ng/mL) and sufficient calcium intake:

• Evaluate for chronic kidney disease with more detailed renal function testing 1, 6
• Consider malabsorption syndromes (celiac disease, inflammatory bowel disease) 4
• Assess for medications that may affect calcium/PTH metabolism (loop diuretics, bisphosphonates) 1
• Rarely, consider normocalcemic primary hyperparathyroidism, though this requires persistent elevation over time and exclusion of all secondary causes 3