# Clinical Cases: Parathyroid Disorders

## 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:

| Criterion | Patient's Value | Meets Criterion? |
|-----------|-----------------|------------------|
| Serum calcium >1 mg/dL above normal | 11.0 mg/dL (0.5 above) | No |
| Age <50 years | 62 years | No |
| eGFR <60 mL/min | 68 mL/min | No |
| T-score <-2.5 at any site | -2.6 at radius | **YES** |
| Vertebral fracture | None | No |
| 24-hr urine Ca >400 mg/day + stone risk | 320 mg/day | No |
| Nephrolithiasis/nephrocalcinosis | None | No |

**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
![Chvostek Sign](case_01_image.jpg)

*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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## Case 2: Post-Thyroidectomy Hypocalcemia and Hypoparathyroidism

### Patient Demographics
- **Age:** 45 years
- **Sex:** Female
- **Occupation:** Marketing executive

### Chief Complaint
"I'm having tingling around my mouth and in my fingers since my thyroid surgery."

### History of Present Illness
A 45-year-old woman presents to the emergency department 36 hours after undergoing total thyroidectomy for a 3.5 cm papillary thyroid carcinoma. She began noticing perioral tingling and paresthesias in her fingertips yesterday evening. This morning, she developed muscle cramps in her hands and feet, and her fingers have been "locking up" into a claw-like position. She feels anxious and has some difficulty catching her breath. The surgery was reported as "uncomplicated," though the surgeon noted the tumor was adherent to surrounding structures requiring careful dissection near the parathyroid glands.

### Physical Examination
- **Vital Signs:** BP 145/88 mmHg, HR 102 bpm, RR 20
- **General:** Anxious, alert, and oriented
- **Neck:** Surgical incision clean, no hematoma
- **Neurologic:**
  - Positive Chvostek sign (facial muscle twitch with tapping over facial nerve)
  - Positive Trousseau sign (carpal spasm with BP cuff inflation to 20 mmHg above systolic for 3 minutes)
  - Carpopedal spasm at rest in hands
  - No altered mental status
  - Perioral and fingertip paresthesias

### Workup
- **Laboratory Studies:**
  - Calcium (total): 6.8 mg/dL (severely low, normal 8.5-10.5)
  - Calcium (ionized): 3.2 mg/dL (severely low)
  - Albumin: 4.0 g/dL (normal)
  - Phosphorus: 5.8 mg/dL (elevated)
  - Magnesium: 2.0 mg/dL (normal)
  - PTH (intact): 6 pg/mL (low, normal 15-65)
  - Creatinine: 0.8 mg/dL (normal)
- **ECG:** Prolonged QT interval (QTc 520 ms)
- **Additional:** Surgical pathology confirms parathyroid tissue was inadvertently removed with thyroid specimen

### Diagnosis
**Symptomatic hypocalcemia** due to **post-surgical hypoparathyroidism**

### Treatment
**IMMEDIATE (Symptomatic Hypocalcemia is an Emergency):**
1. **IV calcium gluconate:**
   - 10% calcium gluconate 20 mL (2 ampules = 186 mg elemental calcium) IV over 10-20 minutes
   - Cardiac monitoring during infusion
   - Repeat bolus if symptoms persist
2. **Continuous IV calcium infusion:**
   - Calcium gluconate 100 mL (10 ampules) in 900 mL D5W at 50 mL/hr
   - Adjust rate based on calcium levels (check q4-6h)
   - Target calcium 8.0-8.5 mg/dL (low-normal to avoid hypercalciuria)
3. **Initiate oral therapy simultaneously:**
   - Calcium carbonate 1500 mg elemental TID with meals (or calcium citrate)
   - Calcitriol 0.5 mcg BID (active vitamin D - essential in hypoparathyroidism)

**WHY CALCITRIOL IS REQUIRED:**
- Without PTH, the kidney cannot convert 25(OH)D to active 1,25(OH)2D
- Calcitriol bypasses this step, providing active hormone directly
- Allows intestinal calcium absorption independent of PTH

**TRANSITION TO CHRONIC MANAGEMENT:**
1. Wean IV calcium as oral therapy takes effect (24-48 hours)
2. Adjust calcitriol dose (0.25-2 mcg daily) to maintain low-normal calcium
3. Maintain calcium supplementation (1-3 g elemental daily in divided doses)
4. Monitor 24-hour urine calcium (target <250 mg/day to avoid nephrolithiasis)
5. Monitor renal function (hypercalciuria risk without PTH)

**LONG-TERM (If Permanent Hypoparathyroidism):**
1. Continued calcium + calcitriol therapy
2. Target serum calcium in low-normal range (8.0-8.5 mg/dL)
3. Monitor for hypercalciuria (increase fluid intake, consider thiazide if elevated)
4. Annual ophthalmologic exam (cataracts)
5. Periodic imaging for basal ganglia calcifications
6. Consider recombinant PTH (Natpara) for refractory cases

**ASSESS RECOVERY:**
1. Trial off calcitriol at 2-3 months (some transient hypoparathyroidism recovers)
2. If hypocalcemia recurs, permanent hypoparathyroidism confirmed
3. Permanent defined as >6 months duration

### Clinical Pearl
Post-surgical hypoparathyroidism is the most common cause of hypoparathyroidism, occurring in up to 30% of total thyroidectomy patients (transient) and 1-3% permanently. The parathyroid glands may be inadvertently removed, devascularized, or contused during surgery. Symptoms of hypocalcemia reflect increased neuromuscular excitability: paresthesias, carpopedal spasm, Chvostek sign (facial twitch with nerve tapping), and Trousseau sign (carpal spasm with ischemia). Severe hypocalcemia can cause seizures, laryngospasm, and cardiac arrhythmias (prolonged QT). IV calcium gluconate is preferred over calcium chloride because it causes less tissue necrosis if extravasated. Calcitriol is essential in hypoparathyroidism because PTH is required to activate vitamin D via renal 1-alpha-hydroxylase. Treatment goals focus on maintaining low-normal calcium to minimize hypercalciuria and preserve renal function, as patients lack the PTH-mediated renal calcium reabsorption.

### Clinical Image
![Chvostek Sign](case_01_image.jpg)

*Demonstration of Chvostek sign elicitation - tapping over the facial nerve causes ipsilateral facial muscle contraction in patients with hypocalcemia due to increased 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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