#19 – Parathyroid Dysfunction



Parathyroid Hormone (PTH)

Parathyroid hormone (PTH) is created and stored in the parathyroid glands and is mainly secreted in response to low serum ionized calcium levels.


PTH increases serum calcium by 3 main mechanisms:

  1. Skeletal Actions
    1. 2 phases
      1. Mobilize calcium from skeletal stores that are immediately accessible
      2. Increase osteoclastic activity
  2. Renal Actions
    1. 3 phases
      1. Increases reabsorption of calcium
        1. Mainly passively in proximal tubule
        2. Can also be actively transported in the cortical thick ascending limb of the loop of Henle and distal convoluted tubules
      2. Inhibits reabsorption of phosphate
        1. Occurs in the proximal tubule
      3. Synthesis of calcitriol
        1. Stimulates synthesis of 1-alpha hydroxylase to convert calcidiol to calcitriol
  3. Intestinal Actions
    1. Increases the intestinal absorption of calcium by calcitriol


Causes of Parathyroid Dysfunction

  • Hyperparathyroidism
    • Primary
      • Hyperfunctioning adenomas (94%)
        • Primarily parathyroid chief cells
      • Glandular hyperplasia (5%)
        • Inferior > superior
      • Carcinoma (1%)
      • Familial hypocalciuric hypercalcemia (FHH)
        • Autosomal dominant defect in calcium-sensing receptor
      • Secondary
        • Chronic renal disease, malabsorption syndromes
  • Hypoparathyroidism
    • Iatrogenic
      • Postsurgical
      • Postradiation
    • Autoimmune
      • Autoimmune polyglandular syndrome
      • Calcium-sensor receptor antibodies
    • Genetic
      • Abnormal development
      • Mutations in calcium-sensing receptor

Signs and Symptoms of Parathyroid Dysfunction

  • Hyperparathyroidism
    • “Stones”
      • Nephrolithiasis (up to 20%)
      • Renal insufficiency
    • “Bones”
      • Decreased bone mineral density
    • “Abdominal groans”
      • Nausea, vomiting, anorexia
      • Peptic ulcer disease
      • Pancreatitis
    • “Porcelain Thrones”
      • Polyuria, constipation
    • “Psychiatric moans”
      • Depression, psychosis, delirium
    • “Fatigue overtones”
      • Lethargy, fatigue
  • Hypoparathyroidism
    • Acute
      • Due to hypocalcemia postsurgery
        • Perioral numbness, paraesthesias, muscle cramps, tetany, Chvostek’s sign, Trousseau’s sign
    • Chronic
      • Basal ganglia calcifications
        • Can cause parkinsonism, dystonia, dementia
      • Cataracts
      • Dental abnormalities (congenital)
        • Dental hypoplasia, defective enamel
      • Dermal
        • Dry, puffy skin
        • Coarse, brittle, and sparse hair
        • Brittle nails

Laboratory Screening

4 main laboratory studies to help differentiate the different causes of parathyroid dysfunction:

  • Serum PTH
  • Serum calcium
  • 24-hour urinary calcium
  • Serum 25-hydroxyvitamin D




Hypercalcemia Work-up


  • Hypoparathyroidism
    • Acute (postsurgical)
      • 10mL ampule of 10% calcium gluconate in 50mL of D5W over 10-20 minutes followed by a calcium gluconate infusion
        • Weaned after calcium ≥ 7.5mg/dL and asymptomatic
      • Oral calcitriol (0.5 mcg BID) and calcium carbonate (0.5-2g BID)
    • Chronic
      • Oral calcium carbonate or citrate 1000-2000 mg/day
      • Oral calcitriol 0.5-2 mcg/day
      • Recombinant human PTH can be used to decrease calcium and vitamin D dosing if patients develop side effects
  • Hyperparathyroidism
    • Primary
      • Surgical Indications (any of these with laboratory findings):
        • Age < 50
        • Serum calcium ≥ 1mg/dL above upper limit of normal
        • DXA T-score ≤ -2.5
        • Vertebral fracture
        • Creatinine clearance < 60 mL/min
        • 24-hour urine calcium ≥ 400 mg/day
        • Presence of nephrolithiasis
      • Preoperative Imaging (Review of parathyroid imaging here)
        • Sestamibi-single photon emission computed tomography (MIBI-SPECT)
          • Allows for visualization of adenoma, hyperactive glands, or ectopic glands prior to surgery
          • Sensitivity – 70-81%, PPV – 91-95%
          • picture1
      • Procedure
        • Bilateral neck exploration
      • Medical
        • Bisphosphonates
          • Inhibits bone resorption and improves bone mass
          • Alendronate
        • Calcimimetics
          • Activate calcium-sensing receptors in the parathyroid gland, which decrease PTH secretion
          • Cinacalcet
        • Vitamin D
    • Secondary
      • Phosphate binders
      • Vitamin D supplementation


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