Parathyroid pathology
Key points
Chief cells synthesise Parathyroid hormone (PTH) when calcium-sensing receptor (CaSR) detects low serum calcium (Ca)
Oxyphil cells have no known function but increase in number with age
Actions of PTH
Increases serum Ca levels
Renal: Limits excretion of calcium in proximal convoluted tubule, converts vitamin D 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol
Acts on osteoclasts to release Ca from bone
Acts on Vitamin D to increase Ca and Phosphate absorption form the gut
Overall decreases phosphate levels
Primary hyperparathyroidism
PTH secretion from:
Parathyroid adenoma or carcinoma
Hyperplasia of all glands
Parathyroid disease from Multiple endocrine neoplasia syndromes (MEN I, IIa)
Must operate even if asymptomatic
Secondary hyperparathyroidism
High PTH to compensate for states of chronic low Ca:
Renal failure
Vit D deficiency
Gut malabsorption
Supplementation (Vit D, Ca, Phos, Mg) + bisphosphonates to treat
Tertiary hyperparathyroidism
Hyperplasia of parathyroid glans in response to chronic secondary hyperparathyroid states
Commonly post renal transplant
Bisphosphonates to treat
Investigations
USS + MRI for adenomas
Sestamibi scan (Technetium-99 uptake by oxyphil cells)
Management
Parathyroidectomy + autotransplant half a gland into sternocleidomastoid or brachioradialis
No need to check Ca levels post op
Should give oral Ca supplements
Neonatal severe hyperparathyroidism
Defect in the CaSR gene
Give Zolendronate as bridge to surgery
Familial hypocalciuric hypercalcaemic disease
Autosomal recessive
Error in calcium sensing receptor
No intervention required
Hypoparathyroidism
Deficiency of PTH, or resistance
Causes:
Congenital e.g. DiGeorge syndrome
Acquired - Post surgical
References
Lofrese JJ, Basit H, Lappin SL. Physiology, Parathyroid. [Updated 2023 Jul 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482510/
Burke JF, Chen H, Gosain A. Parathyroid conditions in childhood. Semin Pediatr Surg. 2014 Apr;23(2):66-70. doi: 10.1053/j.sempedsurg.2014.03.003. Epub 2014 Mar 15. PMID: 24931350; PMCID: PMC5358506.