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. 

The common causes of thyrotoxicosis are shown in Table 41-6.29,30 Thyrotoxicosis can be related to the presence or absence of excess hormone production (hyperthyroidism). Graves disease is the most common cause of hyperthyroidism. Thyrotoxicosis in the elderly is more likely due to toxic thyroid nodules or multinodular goiter than to Graves disease. Excessive intake of thyroid hormone may be due to overtreatment with prescribed therapy. Surreptitious use of thyroid hormones also may occur, especially in health professionals or as a self-remedy for obesity. Thyroid hormones can be obtained easily without a prescription from health food stores or Internet sources. 

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). 

Pituitary TSH suppressants In the treatment or prevention of various types of euthyroid goiters, including thyroid nodules, subacute, or chronic lymphocytic thyroiditis (Hashimoto), multinodular goiter, and in the management of thyroid cancer (except liothyronine). 

TSH suppression in well-differentiated thyroid cancer and thyroid nodules -The target level for TSH suppression in these conditions has not been established in controlled studies. In addition, the efficacy of TSH suppression for benign nodular disease is controversial. Therefore, individualize the dose of levothyroxine used for TSH suppression based on the specific disease and the patient being treated. 

Levothyroxine is taken orally or intravenously and is normally prescribed to treat hypothyroidism or to suppress the release of thyroid hormone so as to manage cancerous thyroid nodules (i.e., thyroid cancer) and growth of goiters. Other less frequently prescribed thyroid and parathyroid drugs include methimazole (Tapazole), various iodides, lithioronine (Triostat), and liotrix (Thyrolar). 

Cooper DS et al Management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid 2006 16 109. [PMID 16420177]... 

Gharib H, Papini E Thyroid nodules Clinical importance, assessment and treatment. Endocrinol Metab Clin North Am 2007 36 707. [PMID 17673125]... 

Young MJ, Serpell JW Management of the solitary thyroid nodule. Oncologist 2008 13 105. 

Thyroid scans with 1l]I are useful in determining the activity of thyroid nodules in the intact thyroid gland. A nonradioactive, cold nodule indicates a higher risk of thyroid carcinoma, but the scan alone is not recommended as a technique of selecting patients for surgery. After removal of a thyroid carcinoma, a scan of the neck may demonstrate areas of increased activity in the cervical lymph nodes and other organs, indicating metastatic disease. 

TPO (ACE, AR, CDPK, ITDI, MLCK, NADH DH, Na+, K+-ATPase, NEP, PKA, PKC, succinate DF1, TOPII,) [antibacterial, AI, anti-thyroid, nodulation signal]... 

Mazzaferri E L1993 Management of a solitary thyroid nodule. New England Journal of Medicine 328 553-559... 

In a study of 53 patients with thyroid nodules, one-dimensional (ID) H MRS distinguished normal thyroid tissue from proven carcinoma of all types with a sensitivity and specificity of 100% (p< 0.0001, Student t-test).15 The basis of the discrimination was altered cellular chemistry reflected in the resonance intensity ratio at a chemical shift of 1.7 ppm (composite with major contribution from lysine) and the methyl groups at 0.9 ppm. The lipid spectral profile is much weaker in adenoma than carcinoma, showing the same trend previously observed for uterine cervix.13... 

Dunn JT. When is a thyroid nodule a sporadic medullary carcinoma (editorial). J Clin Endocrmol Metab 1994 78 824-5. 

Rieu M, Lame MC, Richard A, Lissak B, Lissak B, Sambort B, et al. Prevalence of sporadic medullary thyroid carcinoma the importance of routine measurement of serum calcitonin in the diagnosis and evaluation of thyroid nodules. Clin Endocrinol (Oxf) 1995 42 453-60. 

Ladenson PW. Optimal laboratory testing for diagnosis and monitoring of thyroid nodules, goiter, and thyroid cancer. Clin Chem 1996 42 183-7. 

Haber RS, Weiser KR, Pritsker A, et al. GLUTl glucose transporter expression in benign and malignant thyroid nodules. Thyroid. 1997 7 363-367. 

Finley DJ, Arora N, Zhu B, et al. Molecular profiling distinguishes papillary carcinoma from benign thyroid nodules. J Clin Endocrinol Metab. 2004 89 3214-3223. 

By far the most important investigation for this woman is a fine-needle aspiration biopsy of the thyroid nodule. Frequently, cystic lesions will be drained by this procedure and may not recur. It is important, however, that adequate thyroid epithelium be obtained to enable the diagnosis of thyroid cancer to be excluded or confirmed. 

A 49-year-old woman receiving hormone replacement therapy was found to have a thyroid nodule. No lymphadenopathy was detectable and she appetued clinically to be euthyroid. A technetium scan revealed a cold nodule and an ultrasound scan indicated it was cystic. 

Liothyronine sodium is a thyroid hormone that increases metabolic rate of body tissues and is needed for normal growth and maturation. It is indicated for the replacement or supplemental therapy in hypothyroidism in TSH suppression for treatment or prevention of euthyroid goiters (e.g., thyroid nodules, multinodular goiters, enlargement in chronic thyroiditis) and as a diagnostic agent in suppression tests to differentiate suspected hyperthyroidism from euthyroidism and in treatment of myxedema coma/precoma (IV). 

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. 

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