Autonomous nodules

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. 

RAI is the agent of choice for Graves disease, toxic autonomous nodules, and toxic multinodular goiters. Pregnancy is an absolute contraindication to the use of RAI. 

In fact, IIH, which follows iodine supply normalization, can be viewed as an outcome of iodine deficiency. The deeper the iodine deficiency, the more numerous and more difficult are the IIH cases, which occur after the correction of iodine supply. Also, children form the group that benefits the most from iodine prophylaxis. Some effects of prolonged iodine deficiency, such as the presence of autonomous nodules in the thyroid, seem to be irreversible. However, proper iodine supply lowers the risk of IIH development for other reasons, such as exposure to pharmacological agents with large amounts of iodine. 

The described decline in hyperthyroidism corresponds with observations in Bern (Switzerland), where the incidence of solitary autonomous nodules decreased from 30% to 17% within 9 years after salt iodization (Als et al, 1995). 

In 4 patients the autonomous nodule was not associated with hyperthyroidism in all cases stable iodine was detectable in significant quantities. The partially suppressed contralateral lobe contained iodine in 3 of the 4 patients. 

Nontoxic nodular goiter Autonomous nodule Nontoxic diffuse goiter... 

I agree substantially with the information provided by Dr. Eastman. When we described the Tasmanian epidemic, there was a small number of patients with thyrotoxicosis under the age of 40 years. However, the increment in hyperthyroidism was much more important, about 10 fold, in people over the age of 40 years, and it is true that these patients had autonomous nodules and had been idoine deficient for a very long time. 

In the presence of thyroid disease, and in areas with endemic iodine deficiency, suddenly raising daily iodine intake may precipitate hyperthyroidism, and this has been the subject of some concern as salt iodization efforts proceed with fledgling quality assurance. This effect is felt to be related in part to autonomous nodules in the gland that synthesize and release excess thyroid hormone. The exact prevalence of iodine-induced hyperthyroidism in deficient areas is not clear. Many coim-tries initiating salt iodization programs have reported increases in the incidence of toxic nodular goitre and iodine-induced thyrotoxicosis, usually in older people. While this may be a significant clinical problem, the risk is estimated to be between 0.01 and 0.06% and must be... 

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). 

Tonacchera, M., Agretti, P., Chiovato, L., et al. (2000) Activating thyrotropin receptor mutations are present in nonadenomatous hyperfunctioning nodules of toxic or autonomous multinodular goiter. J. Clin. Endocrinol. Metab. 85, 2270-2274. 

A euthyroid subject with an autonomous adenoma (hot nodule) becomes hyperth)n-oid if given iodide. 

Thyroid hormone is sometimes used to suppress growth in patients with a benign solitary thyroid nodule and a normal TSH, but such therapy generally is not recommended. Suppression therapy is of no value if the nodule is autonomous, as indicated by a subnormal TSH. Once TSH is suppressed, a radioisotope scan should be performed if significant uptake persists, the gland is non-suppressible and L-T,i therapy should be discontinued. Suppression therapy should not be used in patients with known coronary artery disease, since the risks of precipitating cardiac arrhythmias or angina are considerable. 

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

Normal TSH excludes the diagnosis of hyperthyroidism. However, it does not necessarily exclude small autonomous areas in a (nodular) goiter. Larger autonomous areas may be detectable by scintigraphy in patients with palpatory thyroid nodules or goiter and thus at increase risk for IIH in formerly iodine-deficient areas. 

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