Thyroid gland lies over voice box in neck. Thyroid nodule is solitary (single) or multiple lumps felt over middle or side of neck over the thyroid gland. Majority of thyroid nodules do not cause serious condition and may not cause any symptoms. Most thyroid nodules are incidental and found while rubbing the neck by individual or during radiological study, which is performed to rule out other diseases located around neck. Scientific study involving 122 patients suggest solitary or single small thyroid nodule in younger patient more likely have family history of cancer and should be evaluated to rule out cancer. While large thyroid nodule in patients older than 45 years is more likely benign1.
Thyroid gland secretes thyroid hormone. Thyroid nodule is considered as cold, warm or hot. Cold thyroid nodule does not produce any hormone. Similarly thyroid nodule is considered warm or hot depending on amount of thyroid hormone secreted by thyroid tissue forming adenoma. Warm or hot thyroid nodule is also known as follicular adenoma. Patient may suffer with solitary or single thyroid nodule or multiple active thyroid nodule or follicular adenoma. Hard and painful solitary or single adenoma should be evaluated for thyroid cancer or neoplasm.
The thyroid nodule is known as toxic adenoma when thyroid tissue within nodule secretes excessive thyroid hormones. Increased secretion of thyroid hormone often causes symptoms identified as thyroid toxicity. Rarely non-cystic nodules may be filled with blood clots, fibrous tissue or calcium deposits. Cystic nodule is filled with serous fluid and often grows rapidly
Causes of Solitary or Single Thyroid Nodule
Solitary or Single Thyroid Nodule Caused Due to Hypertrophy of Thyroid Tissue- In most cases normal thyroid tissue within thyroid nodule becomes active and increases in size resulting in nodule formation. The condition is benign when gland does not secrete any additional thyroid hormone. Such condition of thyroid nodule is considered as cold nodule. The hormone secreting thyroid nodule is identified as warm or hot adenoma. Hot thyroid nodule secretes higher volume of thyroid hormone than warm thyroid nodule. The condition is often asymptomatic when single warm or hot nodule secretes marginally excess thyroid hormone. The multiple thyroid hormone secreting nodules may cause symptoms of hyperthyroidism.
Iodine Deficiency- Iodine deficiency often causes nodular thyroid disease resulting in solitary or single thyroid nodule. Iodine deficiency is rare in developed country. Iodine deficiency resulting in thyroid nodule is extremely rare in Australia, Canada, USA or Europe. The comparative study in Belgium, which was published in scientific journal suggests iodine deficiency in childhood leads to thyroid nodule formation and need for aggressive treatment2.
Inflammation of Thyroid Gland- Thyroid gland inflammation is known as thyroiditis. Inflammation of single or multiple thyroid nodules causes decreased secretion of thyroid hormone within the nodule. Long-term chronic inflammation of thyroid gland causes Hashimoto’s disease. Hashimoto’s disease is associated with fibrosis of thyroid nodule and surrounding thyroid tissue. Disease results in loss of hormone producing thyroid gland cells. Reduction in significant quantity of thyroid hormone results in condition known as hypothyroidism or myxedema.
Cystic Cause of Solitary or Single Thyroid Nodule- Degenerative changes in hypertrophied thyroid adenoma or normal thyroid gland causes cystic swelling. The cyst is filled with fluid and thyroid cells. The surrounding thyroid tissue may be covered by calcified particles. Cystic swelling may not secrete any thyroid hormone. The cancerous growth within cystic nodule of thyroid has been published and extremely rare3.
Neoplasm- Cancer of thyroid gland is rare. But if thyroid nodule is single and painful then neoplasm or cancer of nodule should be ruled out by performing biopsy and microscopic study. Metastasis to single thyroid nodule is uncommon. Though a case report published in scientific journal suggests kidney cancer was found metastasize as a single solitary thyroid nodule4.
Clinical, sonographic and cytological evaluation of small versus large thyroid nodules.
Taddesse A1, Yaqub A.
J Pak Med Assoc. 2011 May;61(5):466-9.
Does a small difference in iodine status among children in two regions of Belgium translate into a different prevalence of thyroid nodular diseases in adults?
Vandevijvere S1, Dramaix M, Moreno-Reyes R.
Unusual presentation of metastatic adenoid cystic carcinoma: a challenge in aspiration cytology of the thyroid.
Rocca BJ, Barone A, Ginori A, Ambrosio MR, Disanto A.
Pathologica. 2014 Dec;106(4):342-4.
Thyroid nodule: not as clear-cut as it seems.
Bader G1, Puzanov I2, Chakraborty K3.
J Community Support Oncol. 2016 Jan;14(1):45-8. doi: 10.12788/jcso.0184.\
Eur J Nutr. 2012 Jun;51(4):477-82. doi: 10.1007/s00394-011-0232-1. Epub 2011 Aug 7.