What is the diagnosis and plan of care for an elderly female patient with hypothyroidism (elevated TSH), vitamin D deficiency, hypercalcemia, and elevated intact Parathyroid Hormone (PTH) and triglycerides?

Diagnosis and Plan of Care

This patient has primary hyperparathyroidism with concurrent vitamin D deficiency and hypothyroidism requiring immediate initiation of levothyroxine, cautious vitamin D supplementation with close monitoring, and endocrinology referral for surgical evaluation. 1, 2

Primary Diagnosis: Primary Hyperparathyroidism

The combination of hypercalcemia (calcium 10.8 mg/dL) with an inappropriately normal or elevated PTH (34 pg/mL) confirms primary hyperparathyroidism, as PTH should be suppressed in the presence of elevated calcium. 1, 2

• In healthy individuals, any hypercalcemia from non-parathyroid causes should suppress PTH to undetectable or very low levels 2
• A "normal" PTH in the presence of elevated calcium is physiologically inappropriate and diagnostic of primary hyperparathyroidism 2
• The elevated triglycerides (194 mg/dL) may represent concurrent metabolic dysfunction but are not directly related to the hyperparathyroidism 3

Secondary Diagnosis: Primary Hypothyroidism

The markedly elevated TSH (14.100 mIU/L) indicates overt primary hypothyroidism requiring immediate treatment. 4

• Thyroid disease is common in elderly patients and symptoms may overlap with those of hyperparathyroidism 3
• Standard levothyroxine replacement is effective and should be initiated promptly 3

Tertiary Finding: Vitamin D Deficiency

Vitamin D level of 22.9 ng/mL represents insufficiency (target >30 ng/mL) and is commonly seen in primary hyperparathyroidism, potentially exacerbating the disease severity. 3, 5, 6

• Vitamin D deficiency can cause serum calcium to fall into the normal range, leading to diagnostic uncertainty in hyperparathyroidism 6
• Vitamin D deficiency exacerbates primary hyperparathyroidism and vice versa 5, 6

Immediate Management Plan

1. Initiate Levothyroxine for Hypothyroidism

Start levothyroxine 1.6 mcg/kg/day (approximately 75-100 mcg daily for most elderly females) and monitor TSH in 6-8 weeks. 4

• In adult patients with primary hypothyroidism, monitor serum TSH levels after an interval of 6 to 8 weeks after any change in dosage 4
• Once stable, evaluate clinical and biochemical response every 6 to 12 months 4

2. Address Vitamin D Deficiency with Caution

Initiate conservative vitamin D supplementation with 1,000 IU daily (NOT high-dose weekly therapy) given the concurrent hypercalcemia. 3, 5, 7

• High-dose vitamin D (50,000 IU weekly) can exacerbate hypercalcemia and hypercalciuria in patients with primary hyperparathyroidism 7
• Modest daily dosing (1,000 IU) is safer than weekly high-dose regimens in this population 7
• Preliminary data suggest vitamin D repletion in mild primary hyperparathyroidism does not exacerbate hypercalcemia when done carefully 5, 8

Monitor serum calcium and 24-hour urinary calcium excretion closely during vitamin D repletion. 5, 7, 8

• Some patients may experience increased urinary calcium excretion exceeding 400 mg/day after vitamin D repletion 8
• Check serum calcium every 2-4 weeks initially during vitamin D supplementation 7
• Discontinue vitamin D immediately if calcium exceeds 10.2 mg/dL during treatment 1

3. Endocrinology Referral and Surgical Evaluation

Refer to endocrinology and an experienced parathyroid surgeon for surgical evaluation, as this patient likely meets criteria for parathyroidectomy. 1

• Surgical indications include: age <50 years, corrected calcium >1 mg/dL above upper limit of normal, GFR <60 mL/min/1.73 m², osteoporosis, or history of kidney stones 1, 2
• Parathyroidectomy is the only curative treatment for primary hyperparathyroidism 3

4. Additional Diagnostic Workup

Order the following tests before surgical consultation: 1

• Serum creatinine and estimated GFR to assess kidney function 1
• 24-hour urine calcium or spot urine calcium/creatinine ratio to evaluate urinary calcium excretion 1
• Bone density scan (DEXA) to assess for osteoporosis 1
• Renal ultrasonography to assess for nephrocalcinosis or kidney stones 1

5. Monitoring Schedule

Establish the following monitoring protocol: 3, 1, 4

• Serum calcium and phosphorus: every 2-4 weeks initially during vitamin D supplementation, then every 3 months once stable 3, 1
• TSH: 6-8 weeks after initiating levothyroxine, then every 6-12 months once stable 4
• 25-hydroxyvitamin D: recheck in 8-12 weeks to assess response to supplementation 3
• PTH: recheck with calcium levels to monitor disease progression 3

Critical Pitfalls to Avoid

Do NOT use high-dose weekly vitamin D (50,000 IU) in this patient with concurrent hypercalcemia, as this can dangerously exacerbate hypercalcemia and hypercalciuria. 7

Do NOT delay treatment of hypothyroidism while addressing the hyperparathyroidism, as both conditions require concurrent management. 3

Do NOT assume this is secondary hyperparathyroidism based on the elevated PTH alone—the presence of hypercalcemia distinguishes primary from secondary hyperparathyroidism, which presents with hypocalcemia or normal calcium. 1, 2

Do NOT order parathyroid imaging (ultrasound or sestamibi scan) before confirming the biochemical diagnosis and deciding on surgery, as imaging is for surgical planning, not diagnosis. 1

Be aware that vitamin D deficiency in primary hyperparathyroidism increases the risk of postoperative hypocalcemia and "hungry bone syndrome" after parathyroidectomy, underscoring the importance of cautious preoperative vitamin D repletion. 6