Description of the condition
A thyroid nodule is a discrete lesion within the thyroid gland that is palpable and ultrasonographically distinct from the surrounding thyroid parenchyma (ATA 2006). The thyroid nodules are divided into cysts, inflammatory nodules, tumoral nodules (benign, malignant) and may present as proliferatives nodular goiter (CSE 2007). Thyroid nodules are a common clinical problem. The incidence of nodular thyroid disease varies among different populations around the world. In iodine sufficient areas, for instance, palpable thyroid nodules are found in about 4% to 7% of the population, while they are even more prevalent in individuals living in areas of iodine deficiency (Hegedüs 2004). The use of newer high-sensitivity neck ultrasonography has increased the number of detectable thyroid nodules (Massoll 2002), resulting in a very high prevalence (70%) of nodules within the general population (Shimura 2005). Thyroid nodules are more common as age increases and as iodine intake decreases, and they occur more frequently in women (Lansford 2006). There are 3% to 7% of the population with palpable thyroid nodules found in China, however high-resolution ultrasound can detect thyroid nodules in 20% to 70% of the population (CSE 2007). Therefore, we are now facing an 'epidemic' of thyroid nodules.
Most thyroid nodules are asymptomatic and people often find them incidentally on physical examination or self-palpation or incidentally on imaging studies performed for unrelated reasons. A minority of patients with thyroid nodules have thyroid dysfunction, while some patients with thyroid nodules show obstructive symptoms. Although the incidence of malignancy is only about 5% of all nodules (Hegedüs 2004), the clinical importance of newly diagnosed thyroid nodules is primarily the exclusion of thyroid malignant lesion (Belfiore 1989; Hegedüs 2004; Tan 1997). Thyroid malignancy may be associated with the following: clinical features (1) historical features: young (less than 20 years) or old (greater than 60 years) age, male sex, neck irradiation during childhood or adolescence, rapid growth, recent changes in speaking, breathing or swallowing, family history of thyroid malignancy or multiple endocrine neoplasia type 2; (2) physical examination: firm and irregular consistency of nodule, fixation to underlying or overlying tissues, vocal cord paralysis, regional lymphadenopathy; ultrasound findings: (1) hypoechoic lesions, irregular margins, presence of calcifications, absence of halo, internal or central blood flow; (2) low suspicion: echo-free (cystic) lesion, homogeneously hyperechoic lesions (Henry 2008).
Thyroid-stimulating hormone (TSH), thyroid ultrasound and fine-needle aspiration biopsy (FNAB) are key tests to help differentiate malignant from benign lesions. The diagnosis of thyroid nodule malignancy is established through history and physical examination, followed by ultrasonography, FNAB and evaluation of the sample by an experienced cytologist (Hegedüs 2003). With the discovery of a thyroid nodule larger than 1 cm to 1.5 cm in any diameter, one may use serum TSH and free thyroid hormone concentrations as a first-line screening test (Henry 2008). With an elevated TSH level, measurement of serum anti-thyroid peroxidase (anti-TPO) antibody and anti-thyroglobulin (anti-Tg) antibody levels may be helpful for diagnosis of chronic autoimmune thyroiditis (Tan 1997). If the serum TSH is subnormal, one should obtain a radionuclide thyroid scan to document whether the nodule is functioning, shows dysfunction ('warm'), or is non-functioning ('cold'). Functioning nodules rarely harbour malignancy (ATA 2006). Calcitonin may be a useful serum marker of medullary thyroid carcinoma (Cohen 2000). A baseline serum calcitonin value of 10 to 100 pg/mL is abnormal (normal baseline less than 10 pg/mL) and should result in further investigations; values that exceed 100 pg/mL are highly suggestive of medullary thyroid carcinoma (AACE/AME 2006). Computerised tomography (CT) scanning and magnetic resonance imaging (MRI) in the initial diagnosis of thyroid malignancy do not provide higher quality images of the thyroid and cervical nodes than ultrasonography. CT examination of the lower central neck is preferable when tracheal or mediastinal invasion is suspected (Hegedüs 2003). FNAB of thyroid nodules has eclipsed all other techniques for diagnosing thyroid cancer, with reported overall rates of sensitivity and specificity exceeding 90% in iodine-sufficient geographical areas (Henry 2008).
Description of the intervention
All current therapies are effective, but all have their problems. In China and many other countries, doctors use Chinese herbal medicines (CHM) to treat many diseases including thyroid nodules. The contents of traditional Chinese herbal preparations are variable depending on traditional Chinese medicine syndromes of patients. CHM for treating thyroid nodules include Milkvetch, Codonopsis Pilosula, Figwort root, Pangolin Scales, Selfheal, Chinese Thorowax root, Nutgrass Galingale Rhizome, Seaweed, Laminaria Tents, Musk and others. They are made into a Chinese proprietary medicine or a compound of several herbs irrespective of preparation. Besides the traditional herbal decoction (remaining liquid prepared by boiling a mixture of different herbal medicine), there are various forms of herbal medicines such as patent medicine (fixed formula of Chinese medicines in different forms, such as granules, tablets, capsules, or liquids) (Sun 2007), and extracts of herbal medicine (Song 2006), for example Selfheal oral liquid (liquid prepared by boiling Selfheal).
How the intervention might work
Clinical studies from the Chinese literature show that Chinese herbal preparations might shrink the thyroid nodules without significant adverse effects (Tan 2011; Wu 2010; Zhang 2006a). According to the theory of Chinese medicine, practitioners recognise that thyroid nodules are due to blood stasis, Qi stagnation and phlegm coagulation. There are several explanations for CHMs' effects inhibiting the proliferation of thyroid nodule cells: 1. decreased sensitivity of thyroid nodule cells to TSH; 2. decreased activity of TSH; 3. induced apoptosis of thyroid nodule cells; and 4. direct injury of thyroid nodule cells (Zhang 2006b). Herbal preparations are prescribed by practitioners based on the patients' symptoms and observation of the tongue and pulse, so there is a great deal of variation in the use of herbal preparations (Liu 2009).
Why it is important to do this review
Up to now, there are many published studies about the effects of CHM for thyroid nodules (Tan 2011; Wu 2010; Zhang 2006a). However the quality and results of these studies have not been systematically reviewed. There is no systematic review on CHM for benign thyroid nodules in adults so far. Therefore, we aim to assess the existing evidence of CHM for the treatment of benign thyroid nodules.