Lec 2 endocrine thyroid 2

Lec: 2 Dr. Mohammed Alhamdany
(continue) Thyrotoxicosis
Investigations
The first-line investigations are serum T3, T4 and TSH. If abnormal values are found, the tests should be repeated and the abnormality confirmed in view of the likely need for prolonged medical treatment or destructive therapy.
In most patients, serum T3 and T4 are both elevated, but T4 is in the upper part of the reference range and T3 raised (T3 toxicosis) in about 5%.
Serum TSH is undetectable in primary thyrotoxicosis, but values can be raised in the secondary thyrotoxicosis.
An ECG may demonstrate sinus tachycardia or atrial fibrillation.
Further investigations should be undertaken to determine the underlying cause, including measurement of TSH receptor antibodies (TRAb, elevated in Graves’ disease), isotope scanning (99mtechnetium scintigraphy) as shown below: (approach to the patient with thyrotoxicosis)
to differentiate between thyroiditis and factious thyrotoxicosis (extrathyroidal T4), we have to do:
1- T4:T3 ratio (normally 30/1 while in factious hyperthyroidism is up to 70/1.
2- thyroglobuline level (undetectable in factious hyperthyroidism and high in thyroiditis).