Types of Hypoparathyroidism
Hypoparathyroidism can be classified into several distinct types based on etiology, with postsurgical hypoparathyroidism being the most common form, accounting for approximately 75% of all cases. 1
Main Categories of Hypoparathyroidism
1. Postsurgical Hypoparathyroidism
- Results from damage to or removal of parathyroid glands during neck surgery
- Most common cause (75% of cases) 2
- Considered chronic if persisting more than 6 months after surgery 1
- Common surgeries leading to this condition:
- Thyroidectomy
- Parathyroidectomy
- Lymph node dissection
- Cancer neck dissection
2. Genetic Hypoparathyroidism
Disorders of Parathyroid Development
- DiGeorge syndrome/22q11.2 deletion syndrome 3
- Other genetic syndromes affecting parathyroid organogenesis
Disorders of Parathyroid Function
- Activating mutations of the calcium-sensing receptor
- PTH gene mutations
- Autoimmune polyendocrine syndromes
3. Autoimmune Hypoparathyroidism
- Can occur in isolation or as part of autoimmune polyendocrine syndromes
- Autoimmune polyendocrine syndrome type-1 (APS-1): defined by at least two of the following: hypoparathyroidism, chronic mucocutaneous candidiasis, and adrenal insufficiency 4
- Autoimmune polyendocrine syndrome type-2 (APS-2): includes hypoparathyroidism with other autoimmune conditions
4. Functional Hypoparathyroidism
- Magnesium-Related
- Hypomagnesemia: impairs PTH secretion
- Hypermagnesemia: suppresses PTH secretion
- Must be ruled out before pursuing genetic testing 1
5. Infiltrative Disorders
- Destruction of parathyroid tissue by:
- Metastatic cancer
- Iron overload (hemochromatosis)
- Copper overload (Wilson's disease)
6. Radiation-Induced Hypoparathyroidism
- Following radiation therapy to the neck
Clinical Presentation Patterns
Hypoparathyroidism can present as:
- Isolated hypoparathyroidism: occurs as the sole disease in an individual
- Syndromic hypoparathyroidism: associated with other manifestations within complex syndromes 1
Biochemical Profile
All types share similar laboratory findings:
- Hypocalcemia
- Hyperphosphatemia
- Low or inappropriately normal PTH levels (except in pseudohypoparathyroidism where PTH is elevated) 5
- Low 1,25-dihydroxyvitamin D levels 6
Clinical Implications
The underlying cause of hypoparathyroidism affects treatment approach and prognosis:
- Postsurgical cases may require lifelong calcium and vitamin D supplementation
- Genetic cases often need comprehensive management of associated conditions
- Magnesium-related cases may resolve with correction of magnesium levels
Understanding the specific type of hypoparathyroidism is critical for determining appropriate treatment strategies and monitoring protocols, as well as for counseling patients about long-term prognosis and potential complications.