Thyroid Nodules: Symptoms, Causes, Types and Risk factors

Thyroud nodule a small growth that develops within the tissues of the thyroid gland. Most thyroid nodules, around 90 percent, are not cancerous. Thyroid nodules, like other thyroid disorders, are significantly more common in women than men and become more common with advancing age. Endocrinologists call a "hot" thyroid nodule when its tissue secretes thyroid hormones and "cold" when it does not. Most malignant (cancerous) thyroid nodules are cold, while almost all hot nodules are benign (non-cancerous)

What are thyroid Nodules?

Thyroid nodules are lumps and is an abnormal growth of thyroid cells in the thyroid (Endocrine system), which can be hyperplastic or neoplastic. Thyroid nodules are common and generally benign in the sense that they are not cancerous. However, one or more nodules can become hyperactive and produce too much thyroid hormone

Solitary or multiple thyroid nodules increase in frequency with advancing age. 90% of women over the age of 60 and 60% of men over the age of 80 have a nodular thyroid gland. Thyroid nodules in asymptomatic individuals (incidentalomas) are often identified by ultrasound rather than examination of the gland by palpation

Symptoms of Thyroid Nodules

Most thyroid nodules don't cause symptoms. The person may notice a lump on the front of the neck when looking in the mirror. Often, the doctor detects a thyroid nodule during a routine medical examination

• Difficulty breathing and difficulty swallowing
• Hoarseness voice
• Pain in the neck
• Enlarged thyroid gland, known as Goiter

Thyroid nodules can excessively secrete thyroid hormones, causing symptoms of hyperthyroidism. Symptoms of hyperfunction include:

• Nervousness and excess anxiety
• Difficulty sleeping
• Shortness of breath
• Rapid or irregular heartbeat, known as heart palpitations
• Unexplained weight loss
• Increase or decrease in appetite
• Vision problems
• Thinning hair, itching and redness of the skin
• Sensitivity to heat
• Mild or missed menstrual periods
• Muscle weakness, tremors

Thyroid nodules may also be accompanied by a decrease in thyroid hormone levels, resulting in symptoms of hypothyroidism. Symptoms of hypofunction include:

• Fatigue (acute tiredness)
• Heavy menstrual periods
• Poor memory
• Overweight
• Dry skin and brittle hair, which causes hair loss
• Difficulty living in low temperatures
• Muscle weakness and irritability
• Intestinal problems: constipation
• Depression
• Edema or generalized swelling

Causes of Thyroid Nodules

Overgrowth of normal thyroid tissue: thyroid nodules disease is characterized by disordered growth of thyroid cells. The main objective in the evaluation of thyroid nodules is to exclude the presence of thyroid carcinoma, present in about 5% of the thyroid nodules. Nodules are often generated in people with a family history of nodules and in people with iodine deficiency

Iodine deficiency: Iodine is an essential component of the thyroid hormones (TH), thyroxine (T4) and triiodothyronine (T3). Its deficiency causes inadequate production of these hormones, which in turn leads to  develop thyroid nodules, the factor causing iodine deficiency is a low dietary iodine intake. This is most common in areas where the soil is low in iodine

Types of Thyroid Nodules

• Colloid nodules: nodular thyroid disease results from an increase in the rate of proliferation of thyroid cells. Thyroid nodules are generally benign colloid nodules, not cancerous nodules

• Thyroid cyst: thyroid cystic lesions with a predominant fluid component are a common finding, accounting for up to 32% of all thyroid nodules. Pure thyroid cysts are less frequent and correspond to about 1% of thyroid nodules. Most of these nodules are asymptomatic. Sometimes they can cause compression or aesthetic discomfort

• Inflammatory nodules: Hashimoto's thyroiditis is a chronic autoimmune inflammation of the thyroid gland and produces enlarged nodules, with lymphocytic infiltration. Hashimoto's thyroiditis is often related to hypothyroidism

• Multinodular goiter: a patient may have a multinodular goiter (MNG) in which thyroid nodules (usually hyperplastic) replace most of the normal thyroid parenchyma; This presentation is most common in borderline areas of iodine deficiency

• Hyperfunctional Thyroid Nodules: Hyperfunctional thyroid nodules (hot nodules) on thyroid scan, also known as autonomously functioning thyroid nodules (AFTN) without feedback control, which cause the development of hyperthyroidism, are often considered benign

• Thyroid cancer: the main objective in the evaluation of thyroid nodules is to exclude the presence of thyroid carcinoma, present in about 5% of the thyroid nodules

Risk factors of Thyroid Nodules

The clinical relevance of thyroid nodules rests in the detection of or ruling out thyroid nodules depending on :

• Family history suggestive of thyroid cancer or multiple endocrine neoplasia
• Age: under 30 or over 60 years
• Sex: women are more likely than men to develop thyroid nodules
• Characteristics of the nodule, selective criteria for surgery and presence of risk factors

In evaluating a thyroid nodule, factors in history that predict cancerous thyroid nodules include:

• Compression symptoms include dysphagia, dysphonia, hoarseness,  cough and dyspnea

• Rapid growth,  increasing size of nodule 4 cm

• History of childhood head and neck irradiation

• Whole body irradiation by bone marrow transplantation

• History of exposure to radiation fallout in childhood or adolescence can be from prior head and neck irradiation for lymphoma or benign conditions (acne, thymus, enlarged adenoids, tinea capitis),but not from diagnostic procedures, such as a CT scan

• Thyroid cancer syndromes (Familial polyposis, Cowden’s syndrome, Multiple endocrine neoplasia type 2 [MEN-2], Werner syndrome) in a fi rst degree relative