Autonomously functioning thyroid

In multinodular goiters, a thyroid scan shows patchy areas of autonomously functioning thyroid tissue. 

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

Radloiodlne Treatment Radioiodine therapy is particularly well-suited for the treatment of autonomously functioning thyroid tissue. Radioactive iodine, like the natural element, is taken up by the thyroid gland via an active process (the sodium iodide symporter) and accumulates within the thyroid gland. The therapeutic effect occurs as a result of tissue destruction (radiation thyroiditis) caused by short-reached (3 radiation detection is enabled due to emission of a small portion of irradiation. The radioactive material is selectively trapped by the more active autonomously functioning cells and, to a lesser extent, by normal thyrocytes, which depend on TSH stimulation to increase iodine uptake. 

In multinodular goiters (Plummer s disease), follicles with a high degree of autonomous function coexist with normal or even nonfunctioning follicles. Thyrotoxicosis occurs when the autonomous follicles generate more thyroid hormone than is required. 

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. 

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. 

Gennart J-P, Bernard A, Lauwerys R. 1992a. Assessment of thyroid, testes, kidney and autonomic nervous system function in lead-exposed workers. Int Arch Occup Environ Health 64 49-57. 

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). 

In another recent example, Hashimoto reported photoaffinity experiments on retinoic acid receptors (RAR). Retinoic acid plays a critical role in cell proliferation and differentiation. RARs belong to the superfamily of nuclear/ thyroid hormone receptors. They consist of six transmembrane domains (A-F) which is a general feature of these receptors. The A/B domains have an autonomous transactivation function while the C-domain contains the Zn-finger, which binds to DNA. The large E-domain participates in ligand binding, dimerization, and ligand dependent transactivation. Finally, D- and F-domains help the orientation and stabilization of the E-domain. 

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). 

Ermans A.M., Camus M. 1972. Modifications of thyroid function induced by chronic administration of iodide in the presence of "autonomous" thyroid tissue. Acta Endocrinol. 70 463-475. ... 

---