**2. Epidemiology**

Thyroid nodules are a common finding in general population. This is likely due to the increased use of diagnostic imaging for purposes unrelated to the thyroid. The prevalence of thyroid nodules in a population depends on the screening method used and the presence of risk factors for nodule development. The prevalence of thyroid nodules by palpation was found to be 4.2% in a population-based study in Framingham. The prevalence in females and males was 6.4 and 1.5%, respectively [5]. Clinically nonpalpable nodules are frequently identified on ultrasonography and are termed "incidentalomas." The prevalence of thyroid nodules as detected by high resolution ultrasound can be as high as 67% [6]. The prevalence in this Californian study also had an asymmetrical distribution with 72 and 41% prevalence in females and males respectively. 22% patients had solitary nodules, whereas 45% had multiple nodules. In another Italian study by Bartollota et al., the prevalence of thyroid nodules by ultrasonography was 33.1%. Thus it becomes a difficult dilemma on what to do with incidentally detected thyroid nodules which are not malignant and not well-characterised.

Also the number of detected nodules increases with age, with the highest prevalence in the seventh decade. Autopsy studies provide the true prevalence of the incidence in a population. An autopsy study in Mayo clinic revealed a prevalence of around 50% even in patients with no history of thyroid disease [7, 8]. This makes it even more complicated that many individuals would complete their lifespan without any intervention for their thyroid nodules.

### **3. Risk factors**

The prevalence of thyroid nodules is 4 times more common in females than in males. Gender disparity is postulated to occur secondary to influence of oestrogen and progesterone, as demonstrated by increased risk associated with pregnancy and multiparity [9]. The prevalence of thyroid nodules increases with age. Nodules occur more commonly in areas of iodine deficiency. Cigarette smoking can also predispose to development of nodular goitre. This can occur secondary to inhibition of iodine uptake and organification by thiocyanate, which is derived from cyanide in cigarette smoke, hence mimicking iodine deficiency [10]. Obesity has also been demonstrated to be associated with increased risk of goitre and thyroid nodules [11, 12]. Serum IGF-1, being a potent mitogenic factor, was postulated to be associated with development of thyroid nodules. A positive association was observed between serum IGF-1 levels and prevalence of thyroid nodules in males in a study by Volzke et al. In a study by Ying Jian Liu et al., serum IGF-1 levels were not found to be significantly different in patients with hot nodules, cystic cold and solid cold nodules. However, in subgroup analysis, patients with thyroid adenoma on FNA were found to be having significantly higher serum IGF1 levels compared to the control group comprising of healthy adults. However no such association was demonstrated in a study by Hsiao et al. [13–15]. On the other hand, alcohol intake has been associated with decreased prevalence of goitre and thyroid nodules [16].

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nodular goitre.

*Thyroid Nodule: Approach and Management DOI: http://dx.doi.org/10.5772/intechopen.91627*

symptoms of the disease [19].

**5. Clinical evaluation**

Hashimotos thyroiditis Colloid adenomas

Follicular adenomas Hurthle cell adenomas

*Aetiology of thyroid nodules.*

Cysts

**Table 1.**

causes have been summarised in **Table 1**.

**Benign causes Malignant causes**

**4. Aetiology**

Autoimmune thyroid diseases are commonly associated with thyroid nodules. Graves disease is associated with nodules in 10–31% of patients. In a Brazilian study, the prevalence of nodules in Graves disease was 27.8%; 19.5% of the nodules harboured thyroid carcinomas, yielding an overall malignancy prevalence of 5% in patients with Graves disease. Younger age and increased thyroid volumes were associated with increased risk for papillary thyroid carcinoma (PTC). This was in contrast to other studies where older age was a risk factor for malignancy [17, 18]. Small thyroid nodules are also commonly associated with Hashimotos thyroiditis. These should be differentiated form pseudonodules resulting from inflammatory infiltrate. Despite the concerns, the US Preventive Services Task Force (USPSTF), which reviews the effectiveness of screening programs in asymptomatic individuals, recommended against screening for thyroid cancer in adults without signs or

Thyroid nodular disease comprises of a wide range of disorders. Colloid nodules, cysts and thyroiditis comprise of 80% of cases, whereas benign follicular neoplasms and thyroid carcinomas account for 10–15% and 5% cases respectively [20]. These

> Papillary thyroid carcinoma (PTC) Follicular thyroid carcinoma (FTC) Medullary thyroid carcinoma (MTC) Anaplastic thyroid carcinoma (ATC) Primary thyroid lymphoma

Metastatic carcinomas (breast, renal, lung, head and neck)

Thyroid nodules can present as anterior neck swelling. Most nodules grow very slowly over years. Patients may also present with history of rapid increase in size, which can be suggestive of a malignancy, or a haemorrhage into a nodule, especially if associated with pain. Significant sized nodules can result in compressive symptoms based on the anatomical structure being compromised. Larger nodules can result in compression of underlying structures leading to symptoms like dyspnoea, dysphagia, and hoarseness of voice with compression of trachea, oesophagus and recurrent laryngeal nerves respectively. Patient can also present with thyroid dysfunction. Younger patients with adenoma and thyrotoxicosis (Toxic adenoma) tend to present with the classical symptoms of thyrotoxicosis like nervousness, weight loss despite increased appetite, tremors, palpitations, heat intolerance and sweating. On the other hand, thyrotoxicosis in elderly can present with non-specific symptoms like anorexia, atrial fibrillation, congestive heart failure, and is difficult to diagnose due to lack of classical symptoms. A hypothyroid presentation with fatigue, constipation, cold intolerance is more indicative of a diagnosis of autoimmune thyroiditis in patients with *Thyroid Nodule: Approach and Management DOI: http://dx.doi.org/10.5772/intechopen.91627*

Autoimmune thyroid diseases are commonly associated with thyroid nodules. Graves disease is associated with nodules in 10–31% of patients. In a Brazilian study, the prevalence of nodules in Graves disease was 27.8%; 19.5% of the nodules harboured thyroid carcinomas, yielding an overall malignancy prevalence of 5% in patients with Graves disease. Younger age and increased thyroid volumes were associated with increased risk for papillary thyroid carcinoma (PTC). This was in contrast to other studies where older age was a risk factor for malignancy [17, 18]. Small thyroid nodules are also commonly associated with Hashimotos thyroiditis. These should be differentiated form pseudonodules resulting from inflammatory infiltrate. Despite the concerns, the US Preventive Services Task Force (USPSTF), which reviews the effectiveness of screening programs in asymptomatic individuals, recommended against screening for thyroid cancer in adults without signs or symptoms of the disease [19].
