[In vitro thyroid diagnosis in surgery of the thyroid]

After a brief outline of the physiology of the thyroid hormones and the laboratory tests measuring thyroid function, the dosage of normalised T4 (T4N) in patients suffering from various thyroid diseases and subjected to surgical operation is discussed. As the fundamental presupposition of thyroid surgery is that the operation is made in conditions of euthyroidism, the use of a quick and reliable preoperative test giving an exact evaluation of the patient's thyrometabolic conditions is necessary. In conclusion it is stated, on the basis of experience acquired in 90 patients operated for various thyriod diseases, that the last thyrometabolic evaluation can be based on T4N dosage.