Thyroid nodules are common growths within the butterfly-shaped thyroid gland, located at the base of the neck. These lumps are often discovered incidentally, and the vast majority (over 90%) are classified as benign, meaning non-cancerous. Hoarseness, or dysphonia, is a change in voice quality that can make the voice sound breathy, raspy, or strained. Given the thyroid gland’s proximity to the voice box, this article explores how a benign nodule can physically interfere with normal voice function.
Understanding How Benign Nodules Affect Voice
Hoarseness caused by a benign thyroid nodule is primarily a mechanical problem, where the physical bulk of the growth interferes with the structures responsible for voice production. The thyroid gland sits directly below the larynx, or voice box, and is situated near the trachea and the nerves that control the vocal cords. When a nodule significantly increases in size, it can exert pressure on these adjacent structures.
The most direct cause of voice change is the compression of the recurrent laryngeal nerve (RLN), which runs behind the thyroid gland and supplies motor function to nearly all the muscles of the larynx. If a large or awkwardly positioned benign nodule presses on this nerve, it can cause nerve irritation or even paralysis of the corresponding vocal cord (vocal cord paresis or paralysis). This prevents the vocal folds from closing properly, resulting in a weak, breathy, or hoarse voice.
It is the size and exact location of the nodule, rather than its benign cellular status, that determines its potential to affect the voice. Nodules that grow toward the back of the thyroid or have a retrosternal extension—meaning they grow down into the chest cavity—are more likely to compress the RLN or displace the trachea. The physical displacement of the trachea and larynx can also alter the acoustics of the voice. However, vocal cord paralysis due to a benign nodule is considered a rare occurrence.
Medical Evaluation of Vocal Changes
When a patient with a known thyroid nodule presents with new or persistent hoarseness, a thorough medical evaluation is necessary to determine the exact cause. This is important because hoarseness can sometimes be an indication of thyroid malignancy, even if a previous nodule was determined to be benign. The initial step involves a physical examination of the neck to assess the size and firmness of the thyroid gland or nodules.
Specialized voice assessments are then performed to visualize the vocal cords and analyze their movement. A procedure called a laryngoscopy or stroboscopy involves inserting a thin, flexible scope to view the larynx. This allows the physician to check for signs of vocal cord paralysis, confirming damage to the recurrent laryngeal nerve, or to see if the nodule is physically displacing the voice box structure.
Follow-up imaging, typically a thyroid ultrasound, is used to precisely measure the nodule and map its relationship to the surrounding anatomy. This imaging confirms if the nodule is large enough to be causing mechanical compression of the trachea or if it is located near the path of the recurrent laryngeal nerve. The overall evaluation aims to differentiate between benign compression and the possibility of nerve infiltration by a cancerous growth. A fine-needle aspiration biopsy may be repeated if new symptoms like hoarseness appear, to definitively rule out a change in the nodule’s character.
Other Potential Causes of Hoarseness
While a thyroid nodule can be the source of hoarseness, voice changes are a common symptom with many different origins unrelated to the thyroid gland. Upper respiratory infections, like the common cold, are the most frequent cause of temporary hoarseness due to inflammation of the vocal cords, known as laryngitis. Overuse or misuse of the voice, common in professions like teaching or singing, can also lead to benign growths on the vocal cords themselves, such as nodules or polyps, which impair vocal function.
Chronic acid reflux, specifically gastroesophageal reflux disease (GERD) or laryngopharyngeal reflux (LPR), causes stomach acid to irritate the delicate tissue of the larynx, leading to persistent hoarseness.
Non-Thyroidal Causes
Other non-thyroidal causes include:
- Allergies
- Smoking
- Certain medications
- Neurological disorders that affect the nerves controlling the vocal muscles
Because hoarseness is a potential red flag for more serious conditions, including laryngeal cancer or, in rare cases, thyroid cancer that has invaded the RLN, a medical evaluation is always warranted.