From the Guidelines
Hypoparathyroidism is primarily caused by damage to or removal of the parathyroid glands during neck surgery, particularly thyroid surgery. This condition can lead to a range of complications, including hypocalcemia, which can be predicted by measuring parathyroid hormone (PTH) levels after surgery 1. According to the Australian Endocrine Surgeons guidelines, PTH measurement is recommended 7 hours after surgery to predict postoperative hypoparathyroidism 1.
Causes of Hypoparathyroidism
- Damage to or removal of the parathyroid glands during neck surgery, particularly thyroid surgery
- Autoimmune disorders where the immune system attacks the parathyroid glands
- Genetic disorders such as DiGeorge syndrome or autoimmune polyglandular syndrome type 1
- Low magnesium levels which impair parathyroid hormone function
- Radiation treatment to the neck
- Heavy metal poisoning
- Infiltrative diseases like hemochromatosis or Wilson's disease
- Idiopathic, meaning the cause is unknown
Importance of PTH Measurement
PTH measurement is crucial in predicting postoperative hypoparathyroidism and hypocalcemia 1. The American Thyroid Association Surgical Affairs Committee recommends that intensive calcium monitoring is not necessary when PTH concentration is above 1.49 pmol/L (14.8 pg/mL) measured 20 minutes after surgery 1. However, it is essential to note that different PTH assays may yield varying results, and absolute cutoff values should be avoided in guidelines 1.
Clinical Implications
Hypoparathyroidism can lead to inadequate production of parathyroid hormone (PTH), resulting in low calcium levels and high phosphorus levels in the body. This can cause symptoms such as muscle cramps, tingling, seizures, and heart rhythm abnormalities. Treatment typically involves calcium and vitamin D supplements to maintain normal calcium levels in the absence of adequate PTH. It is crucial to prioritize the measurement of PTH levels using a consistent assay to ensure accurate diagnosis and treatment of hypoparathyroidism.
From the FDA Drug Label
Patients had hypoparathyroidism for on average 15 years and hypoparathyroidism was caused by post-surgical complications in 71% of cases, idiopathic hypoparathyroidism in 25%, DiGeorge Syndrome in 3%, and auto-immune hypoparathyroidism in 1%.
The causes of hypoparathyroidism include:
- Post-surgical complications (71% of cases)
- Idiopathic hypoparathyroidism (25% of cases)
- DiGeorge Syndrome (3% of cases)
- Auto-immune hypoparathyroidism (1% of cases) 2
From the Research
Causes of Hypoparathyroidism
- The most common cause of hypoparathyroidism is iatrogenic, resulting from removal of, or damage to, the parathyroid glands during anterior neck surgery 3, 4, 5, 6.
- Autoimmune destruction of the parathyroid glands and other genetic causes also represent significant etiologies 3, 4.
- Congenital or acquired disorders, such as destruction or infiltrative disorders of the parathyroids, can also lead to hypoparathyroidism 4.
- Impaired secretion of parathyroid hormone may be seen with hypomagnesemia or hypermagnesemia 4.
Underlying Mechanisms
- Hypoparathyroidism is characterized by hypocalcemia, hyperphosphatemia, and low or undetectable levels of parathyroid hormone (PTH) 3, 4, 5, 6, 7.
- PTH plays a crucial role in regulating calcium homeostasis, vitamin D-dependent calcium absorption, renal calcium reabsorption, and renal phosphate clearance 4, 6.
- The lack of PTH leads to inactive bone accrual without remodeling, and the kidneys lose their calcium-conserving actions, resulting in increased calcium excretion 3.