Parathyroid Conditions

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 PO₄^3-

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 4^th and 5^th digits, round face

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

Diagnosis – Blood test shows decreased Ca²⁺, but ­increased PO₄^3- and ­PTH

– During infusion of PTH, urinary cAMP and PO₄^3- 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 PO₄^3- binds serum Ca²⁺

– Less free calcium stimulates parathyroid glands to secrete excess PTH

Diagnosis – Blood test shows ­increased PTH + ­ALP + ­PO₄^3- 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 PO₄^3- 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