Thyroid-stimulating hormone iodine

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. 

Thilly CH, Swennen B, Bourdoux P, et al. 1993. The epidemiology of iodine-deficiency disorders in relation to goitrogenic factors and thyroid-stimulating-hormone regulation. Am J Clin Nutr 57(2 Suppl) 267S-270S. 

RAIU = radioactive iodine uptake TSH = thyroid-stimulating hormone h"4 uptake method TT4 X RT3LI method ... 

In the adult population, the prevalence of overt hypothyroidism is 19 per 1000 women and 1 per 1000 men with annual incidence of overt hypothyroidism is 4 per 1000 women and 0.6 per 1000 men. Subclinical hypothyroidism is also more common in women, the incidence increases with age, with up to 10% of women older than 60 years having an increased thyroid-stimulating hormone concentration. Subclinical hypothyroidism is more common in people who have been treated for hyperthyroidism with radioactive iodine or surgery, and in those with organ-specific autoimmune diseases, such as pernicious anaemia, type 1 diabetes mellitus, or Addison s disease. 

The effects of iopromide on thyroid function have been investigated in 20 pre-term infants with very low birth weights and 26 matched premature infants who did not receive contrast medium (571). The dose of iopromide (iodine 300 mg/ml) was 0.3-1.0 ml. Iopromide did not affect the concentrations of free thyroxine and thyroid stimulating hormone. This was attributed to the small amount of free iodide that iopromide contains... 

Thyroid-stimulating hormone (TSH) that regulates the growth of the thyroid gland and the iodination of amino acids to produce the thyroid hormones triiodothyronine and thyroxine (see Chapter 52)d... 

Thyroid-stimulating hormone (TSH)—A polypeptide hormone secreted by the anterior pituitary gland that stimulates iodine uptake and thyroid hormone synthesis. 

In 1922, Smith and Smith (S12) found a substance in bovine pituitary glands which activated the thyroid of hypophysectomized tadpoles. For many years this finding was the basis for the assay of what has come to be called thyroid-stimulating hormone (TSH). The mechanism by which TSH stimulates the thyroid to organify iodine and secrete thyroxine has received much attention in recent years. 

E5. Ensor, J. M., and Munro, D. S., A comparison of the influence of thyroid-stimulating hormone and cyclic 3, 5 -adenosine monophosphate on the in vitro release of radio-iodine from the thyroid glands of mice. J. Endocrinol. 38, XXViii (1967). 

Hypothyroidism (thyroid hormone deficiency) may result from autoimmune disease (Hashimoto s disease) or from deficient synthesis of TSH or TRH (thyroid-stimulating hormone-releasing factor). Because adequate ingestion of iodine is a prerequisite for thyroid hormone synthesis, iodine deficiency also causes hypothyroidism. In children, thyroid hormone deficiency (called cretinism) causes depressed growth and mental retardation. Severe hypothyroidism in adults (myxedema) results in symptoms such as edema (abnormal fluid accumulation) and goiter. Hypothyroidism is usually treated with hormone replacement therapy. 

Under the influence of thyroid stimulating hormone (TSH) thyroid hormones are made by attaching iodine to tyrosine. The source of tyrosine is thyroglobulin, a protein synthesized in the thyroid gland. There are two hormones, thyroxine and triiodothyronine, referred to together as thyroid hormone. 

The relative rates of synthetic activity at the various sites depend on the concentration of thyroid-stimulating hormone (TSH) and the availability of iodide, possibly accounting for the varying proportions of U and Tj depending on iodine supply. Limited iodine is utilized more efficiently in the synthesis of Tj, the transcriptionally active form, which contains three-fourths as much iodine as U. Eventually, iodine deficiency impairs synthesis of both and Tj and hypothyroidism results. In addition to the coupling reaction, intrathyroidal and secreted U is generated by the 5 -deiodination ofT,. 

B. Thyroid-Stimulating Hormone (TSH) In thyroid cells, this peptide increases iodine uptake... 

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