Endocrine · Year 2 · from Endocrine

Case 1: Primary Hyperparathyroidism - Asymptomatic Hypercalcemia

Patient Demographics

• Age: 62 years
• Sex: Female
• Occupation: Retired librarian

Chief Complaint

"My doctor said my calcium is high on my blood work."

History of Present Illness

A 62-year-old woman is referred for evaluation of hypercalcemia discovered incidentally on routine health maintenance laboratory testing. Her calcium was 10.8 mg/dL on initial testing and confirmed at 11.0 mg/dL on repeat. She is largely asymptomatic but on detailed questioning reports mild fatigue, occasional constipation, and increased thirst and urination over the past year, which she attributed to aging. She has no history of kidney stones, fractures, or bone pain. She does not take calcium supplements, vitamin D, or thiazide diuretics. Her only medication is amlodipine for hypertension.

Physical Examination

• Vital Signs: BP 138/82 mmHg, HR 74 bpm
• General: Well-appearing woman in no distress
• Neck: No palpable thyroid nodules or masses
• Cardiovascular: Regular rhythm, no murmurs
• Abdomen: Soft, non-tender
• Musculoskeletal: No bone tenderness
• Neurologic: Normal, no focal weakness

Workup

• Laboratory Studies:
• Calcium (total): 11.0 mg/dL (elevated, normal 8.5-10.5)
• Calcium (ionized): 5.8 mg/dL (elevated)
• Albumin: 4.0 g/dL (normal)
• Phosphorus: 2.4 mg/dL (low-normal)
• PTH (intact): 98 pg/mL (elevated, normal 15-65)
• 25-hydroxyvitamin D: 22 ng/mL (insufficient)
• Creatinine: 1.0 mg/dL (normal)
• eGFR: 68 mL/min/1.73m² (mild reduction)
• 24-hour urine calcium: 320 mg/24hr (elevated, normal <250)
• Calcium-to-creatinine clearance ratio: 0.018 (>0.01, argues against FHH)
• Imaging:
• DEXA scan:
• Lumbar spine T-score: -1.4 (osteopenia)
• Total hip T-score: -1.8 (osteopenia)
• Distal 1/3 radius T-score: -2.6 (osteoporosis)
• Renal ultrasound: No nephrolithiasis or nephrocalcinosis
• Parathyroid sestamibi scan: Focal uptake inferior to left thyroid lobe
• Neck ultrasound: 1.2 cm hypoechoic nodule posterior to left lower thyroid pole

Diagnosis

Primary hyperparathyroidism due to parathyroid adenoma (localized to left inferior gland)

Assessment of Surgical Criteria

Per 2022 guidelines, surgery is recommended if ANY of the following present in asymptomatic patients:

Surgical indication: Osteoporosis at distal radius (T-score -2.6)

Treatment

RECOMMENDED: PARATHYROIDECTOMY

1. Pre-operative localization studies: Already completed (sestamibi + ultrasound concordant)
2. Minimally invasive parathyroidectomy (MIP) with focused approach to left inferior gland
3. Intraoperative PTH monitoring (50% drop from baseline confirms successful removal)
4. Expected cure rate: 95-98%

PERIOPERATIVE MANAGEMENT:

1. Vitamin D repletion preoperatively (reduces risk of hungry bone syndrome)
2. Monitor calcium postoperatively (transient hypocalcemia common)
3. Calcium and vitamin D supplementation as needed

POST-OPERATIVE:

1. Confirm eucalcemia at 2 weeks
2. Repeat DEXA at 1-2 years (expect bone density improvement)
3. Annual calcium monitoring

IF SURGERY DECLINED:

1. Ensure adequate hydration
2. Avoid thiazide diuretics (increase calcium)
3. Moderate calcium intake (no severe restriction)
4. Vitamin D repletion (paradoxically may help suppress PTH)
5. Bisphosphonates for osteoporosis (alendronate)
6. Cinacalcet (calcimimetic) if calcium significantly elevated
7. Monitor: Calcium annually, creatinine annually, DEXA every 1-2 years

Clinical Pearl

Primary hyperparathyroidism is the most common cause of hypercalcemia in the outpatient setting, affecting ~1% of postmenopausal women. The biochemical hallmark is hypercalcemia with elevated or "inappropriately normal" PTH - any detectable PTH in the setting of hypercalcemia is abnormal since PTH should be suppressed. Single adenoma accounts for 80-85% of cases. Hypercalciuria with calcium-to-creatinine clearance ratio >0.02 helps distinguish from familial hypocalciuric hypercalcemia (FHH), which should not undergo surgery. Primary HPT preferentially affects cortical bone (distal radius), unlike postmenopausal osteoporosis which primarily affects trabecular bone. Even asymptomatic patients may have end-organ effects warranting surgery, and guidelines provide clear criteria for intervention.

Clinical Image

Illustration demonstrating the technique for eliciting Chvostek sign - tapping over the facial nerve anterior to the ear to assess for hypocalcemia-induced neuromuscular irritability.

Image Source: Wikimedia Commons - "Chvostek sign elicitation" License: CC BY-SA 4.0 URL: https://commons.wikimedia.org/wiki/File:Chvostek_sign_elicitation.png

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