Autonomously functioning thyroid nodules

OHG 8 oxo-Guanosine 8-OHdG 8-oxo-2 -Deoxyguanosine AFTN Autonomously functioning thyroid nodules... 

Thyroid autonomy appears as a solitary toxic nodule or toxic multinodular goitre. In toxic thyroid, the nodule s synthesis and secretion of thyroid hormones is autonomous from the thyroid-stimulating hormone (TSH), which is produced in the pituitary gland. Accordingly TSH is suppressed and the extranodular thyroid tissue is functionally downregulated. Thyroid autonomy occurs frequently in iodine-deficient countries, whereas it is much less common in iodine-sufficient areas. Constitu-tively activating mutations in the TSH receptor and in the Gs a protein are the major molecular aetiology of toxic thyroid nodules. 

An autonomous thyroid nodule (toxic adenoma) is a discrete thyroid mass whose function is independent of pituitary control. Hyperthyroidism usually occurs with larger nodules (i.e., those greater than 3 cm in diameter). 

Toxic adenomas may result in hyperthyroidism with larger nodules. Because there may be isolated elevation of serum T3 with autonomously functioning nodules, a T3 level must be measured to rule out T3 toxicosis if the T4 level is normal. After a radioiodine scan demonstrates that the toxic thyroid adenoma collects more radioiodine than the surrounding tissue, independent function is documented by failure of the autonomous nodule to decrease its iodine uptake during exogenous T3 administration. 

El. Evered, D. C., Clark, F., and Petersen, V. B., Thyroid function in euthyroid subjects with autonomous thyroid nodules. Clin. Eruiocrinol. 3,149-154 (1974). 

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