A 25 year old young woman has recurrent episodes of headache and sweating. Her mother had renal calculi and died after having a neck mass. The physical exaination reveals a thyroid nodule but no clinical sign of thyrotoxicosis. Before performig thyroid surgery, the surgeon should order :
Correct Answer: Serial 24 hours test for catecholamines, metanephrines and vanillylamandelic acid excertion.
Description: Ans. is 'd' i.e. Serial 24 hrs tests for catecholamines, metanephrine and vanillylmandelic acid excretion.This topic is one of the favorites of AIIMS ExaminersIt is a case of MEN Type II a i.e.-Medullary Carcinoma thyroid*Hyperparathyroidism *Pheochromocytoma. *Now lets us see which among the following investigation, the surgeon should order prior to thyroid surgery.Measurement of thyroid hormones :In is of no use as in medullary ca, the level of thyroid hormone is not altered.It secretes calcitonin*So the measurement of calcitonin level in serum after calcium or pentagastrin injection is done to diagnose this cancer.Note that the calcitonin level in serum is helpful in the diagnoses of MCT but it offers no specific advantage to the surgeons just before surgery.Serial determination of serum calcium, phosphorus, proteins and alkaline phosphatase :Hyperpara thyroidism is diagnosed by finding hyper calcemia, hypercalciuria, hypophosphatemia parathyroid hormone. But the diagnoses of hyperparathyroidism is not mandatory before performing surgery for MCT.5 HIA A urinary estimation :has no value here as it is done for the diagnosis of carcinoid syndrome*.Serial 24 hrs test for catecholamines, metanephrine and vanillylmandelic acid excretion :These are done for the diagnosis of pheochromocytoma.Measurement of urinary catecholamine levels is of utmost importance before embarking upon thyroid surgery, because pheochromocytoma secretes large amount of catecholamine which cause hypertension, the secretion is further increased during surgery which causes large swings in B.P and arrhythmias.So if pheochromocytoma is diagnosed before surgery, the dangers may be minimised by preoperative preparation. The effect of catecholamines is blocked by giving a blockers and b blockers prior to surgery.Bailey says "Pheochromocytoma must be excluded by measurement of urinary catecholamine levels in all cases before embracing upon thyroid surgery to avoid the potential hazards associated with this condition. "
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