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Thyroid Nodules- Causes

What causes thyroid nodules?

Although the molecular mechanisms that cause nodules are not fully understood, thyroid nodules are known to be due to either benign or malignant conditions.  There are only a few known risk factors that predispose a person to develop thyroid nodules. Your endocrinologist at Houston Thyroid and Endocrine will review these risk factors with you during your thyroid nodule clinic appointment. It is important to note that the likelihood of ruling out thyroid cancer by risk factors and patient history alone is only 60%.

 If you have a thyroid nodule that needs evaluation please contact our thyroid nodule coordinator


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Risk factors for cancer in a thyroid nodule 
  1. As a patient ages, the rates of thyroid nodularity increase. 
  2. A nodule in a young person (<20 years old) is twice more likely to be a cancer than in an adult. 
  3. The rate of thyroid cancer is higher in men than women. 
  4. Previous radiation treatment to the head and neck region as a child or adolescent. Radiation used to be used to treat acne or tonsil enlargement in the 1950's and 1960's. 
  5. Hematopoietic stem cell transplant increases the rates of thyroid cancer. 
  6. Smoking, especially areas that have iodine deficiency 
  7. A family history of thyroid cancer or family history of mulitple endocrine neoplasia (MEN) type 2 

Factors that suggest a benign cause of a thyroid nodule 
  1. A family history of Hashimoto's thyroiditis, benign nodule, or goiter 
  2. History of hyperthyroidism, especially if a "hot nodule"
  3. A sudden increase in size of the nodule with pain or tenderness, suggesting a cyst or localized thyroiditis.


The benign conditions associated with thyroid nodules


 Multinodular goiters that have "colloid adenomas"  Hashimoto's Thyroiditis, also known as chronic lymphocytic thyroiditis  Thyroid Cysts: colloid, simple, or hemorrhagic Follicular adenomas
 Macrofollicular adenomas Microfollicular or cellular adenomas Hurthle cell adenomas  Macro- or Microfollicular pattern



The malignant conditions associated with thyroid nodules

Papillary Carcinoma Follicular Carcinoma Medullary Carcinoma Hurthle cell type
Anaplastic carcinoma Primary thyroid lymphoma  Metastatic carcinoma (breast, renal cell, etc)  


References: J Clin Endocrinol Metab 1955; 15:1270,   Acta Endocrinol (Copenh) 1989 Aug;121(2):197-202,   Am J Med 1992 Oct;93(4):363-9,   Medicine (Baltimore) 1985 Jan;64(1):1-15, J Clin Oncol. 2007 Jun 10;25(17):2449-54.