Hypoparathyroidism
A condition of deficient parathyroid hormone resulting in low blood calcium levels and high phosphorus levels.
Emergency Management: Severe acute hypocalcemia with tetany or seizures requires IV Calcium Gluconate (1-2 ampules, 10-20 mL of 10% solution) administered slowly over 10-20 minutes, followed by a continuous calcium infusion if needed.
Hypoparathyroidism is an endocrine disorder characterized by absent or inappropriately low levels of parathyroid hormone (PTH), leading to hypocalcemia and hyperphosphatemia. It most commonly occurs iatrogenically following neck surgery.
Detailed Overview
PTH is essential for maintaining serum calcium levels by promoting bone resorption, renal calcium reabsorption, and renal conversion of 25-hydroxyvitamin D to its active form, 1,25-dihydroxyvitamin D. Deficiency leads to neuromuscular irritability, tetany, and long-term complications like basal ganglia calcifications and cataracts.
Epidemiology & Demographics
Prevalence is estimated at 37 per 100,000 in the United States. Around 75% of cases are postoperative. Autoimmune and genetic causes are rare.
Etiological Mechanism
The majority of cases are iatrogenic due to inadvertent damage or removal of the parathyroid glands during thyroidectomy, parathyroidectomy, or radical neck dissection. Non-surgical causes include autoimmune polyendocrine syndrome type 1 (APS-1) and DiGeorge syndrome.
Primary Causes
Anterior neck surgery (post-thyroidectomy)
Autoimmune destruction (often part of APS-1)
Genetic disorders (DiGeorge syndrome - 22q11.2 deletion)
Infiltrative diseases (hemochromatosis, Wilson's disease)
Lack of PTH reduces osteoclastic bone resorption, decreasing calcium release from bone. In the kidneys, low PTH decreases calcium reabsorption in the distal tubule and increases phosphate reabsorption in the proximal tubule. Furthermore, low PTH results in decreased 1-alpha-hydroxylase activity, reducing active 1,25(OH)2 Vitamin D, which severely impairs intestinal calcium absorption. The net result is profound hypocalcemia and hyperphosphatemia.
Diagnostic Criteria & Guidelines
Simultaneous presence of low albumin-corrected serum calcium (or ionized calcium) and low or inappropriately normal intact parathyroid hormone (PTH) levels, in the setting of normal serum magnesium.
1. Oral Calcium: Calcium carbonate 1000-2000 mg or Calcium citrate elemental calcium divided TID with meals. 2. Active Vitamin D: Calcitriol 0.25-1.0 mcg PO twice daily. The goal is to maintain serum calcium in the low-normal range (approx 8.0-8.5 mg/dL) to avoid hypercalciuria.
Second-Line & Adjunctive Therapy
Recombinant human parathyroid hormone (rhPTH [1-84], Natpara) or Teriparatide (rhPTH [1-34]) for patients whose calcium cannot be controlled on standard therapy or who have severe hypercalciuria/renal complications.
Surgical & Procedural Management
Parathyroid autotransplantation may be attempted during initial thyroid surgery to prevent the condition.
Patient Counseling & Advice
Educate the patient to recognize the early signs of hypocalcemia (tingling around the lips/fingers) and keep extra calcium supplements on hand. Advise that target calcium is deliberately kept slightly low to protect the kidneys.
Follow-Up & Monitoring Schedule
Check serum calcium, albumin, phosphorus, and creatinine every 3-6 months once stable. 24-hour urine calcium every 6-12 months, aiming for < 300 mg/24 hours to prevent nephrocalcinosis.
Preventive Strategies
Meticulous surgical technique during thyroidectomy to identify and preserve the parathyroid glands and their blood supply.
Usually excellent with strict adherence to calcium and calcitriol replacement, though patients carry a lifelong burden of medication and monitoring. Renal complications are the primary long-term concern.