Parathyroid Conditions

a) Depletion of PTH

  • Hypoparathyroidism – A condition due to an impairment in PTH secretion

– Primary – due to autoimmune damage, congenital DiGeorge syndrome

– Secondary – due to radiation, surgery or low Mg2+ (needed for synthesis)

 

Symptoms –Resemble hypocalcaemia raising excitability of nerve and muscle:

– Tetany –> muscle twitching, cramping and spasm

– Gives numbness and tingling around mouth (circumoral)

Trousseau sign – inflating cuff above systolic BP –> muscle contraction due to increase excitability

– Chvostek sign – tap on zygomatic bone –> twitching of facial muscle as it is more excitable.

 

Diagnosis – Blood test shows decreased PTH and decreased Ca2+, but ­increased PO43-

Management – Calcium supplements + Alfacalcidol (synthetic Vitamin D3)

 

  • Pseudohypoparathyroidism – this occurs due to a failure of the organs to respond to PTH

– Can be autosomal dominant – characterized by short stature with short 4th and 5th digits, round face

– Alternate form is pseudopseudohypoparathyroidism – same features but with normal biochemistry

 

Diagnosis – Blood test shows decreased Ca2+, but ­increased PO43- and ­PTH

– During infusion of PTH, urinary cAMP and PO43- do not rise unlike in hypoparathyroidism.

 

Management – Calcium supplements + Alfacalcidol (synthetic Vitamin D3)

 

b) Excess of PTH

  • Primary Hyperparathyroidism – Excess PTH due to a disorder of the parathyroid gland itself

Causes:  80% due to parathyroid adenoma, also due to parathyroid hyperplasia or parathyroid carcinoma

 

Symptoms – It often feels asymptomatic, but there are signs related to high serum calcium:

– Bones –> Ectopic calcification (e.g. cornea) and bone pain (due to bone resorption)

– Stones –> Renal stones and renal failure

– Groans –> Abdominal pain, vomiting, constipation and weakness

– Psychic Moans –> Confusion + irritability + Depression

 

Diagnosis – Blood test ­increased PTH (can be normal), ­increased Ca2+, increased ­urinary cAMP, increased ­ALP and decreased PO43-

– Urine Calcium: creatinine clearance ratio > 0.01

– X-ray –> osteitis fibrosa cystica of phalanges + “pepper-pot” skull appearance

 

Treatment – If Ca2+ < 0.25mM above normal limit and no organ damage, conservatively give fluids

– If moderate to severe, surgical total parathyroidectomy or cinacalcet if unsuitable for surgery.

 

  • Secondary Hyperparathyroidism – This is excess PTH due to a disease extrinsic to gland

– The most common cause is chronic renal failure.

– Renal insufficiency gives decreased phosphate excretion so PO43- binds serum Ca2+

– Less free calcium stimulates parathyroid glands to secrete excess PTH

 

Diagnosis – Blood test shows ­increased PTH + ­ALP + ­PO43- but decreased  Ca2+and Vitamin D

Treatment – Vitamin D supplements,  else surgery if bone pain/pruritus/ectopic calcifications

 

  • Tertiary hyperparathyroidism – This occurs after prolonged secondary hyperparathyroidism, causing glands to act autonomously after undergoing hyperplasia, which is seen in chronic renal failure

– Lead to increased Ca2+ from unlimited PTH secretion

– ­increased PTH, ­Ca2+, ­urinary cAMP, ­ALP                                      – decreased PO43- and Vitamin D

 

  • Malignant hyperparathyroidism

Parathyroid-related protein is produced by some squamous cell lung, breast and renal carcinomas

– This protein mimics PTH resulting in increased calcium

Treatment – Need to treat the underlying cancer

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