Hypothyroidism is a common endocrine disorder where the thyroid gland does not produce enough hormones to meet the body’s needs. This deficiency slows down metabolism and affects nearly every system, often causing fatigue, weight gain, and cold intolerance. Although a persistent cough might seem unrelated, many people with an underactive thyroid report this specific respiratory symptom. The connection between low thyroid hormone and a chronic cough involves both the direct physiological effects of the deficiency and the secondary conditions it triggers.
The Direct Link: Hypothyroidism and Cough Causation
Low levels of thyroid hormone can directly impact throat and respiratory tract tissues through a process known as myxedema. Myxedema involves the abnormal deposition of mucopolysaccharides and proteins within the subepithelial spaces of tissues, including the larynx and pharynx. This accumulation causes localized swelling and edema, leading to a thickening of the vocal cords and pharyngeal mucous membranes.
Laryngeal swelling results in hoarseness, voice changes, and a frequent sensation of having a lump in the throat, medically termed globus sensation. This constant feeling of irritation often triggers a reflexive, dry, and persistent cough or the need for frequent throat clearing. In cases of severe hypothyroidism, respiratory muscle strength can decrease, impairing the function of the diaphragm and other muscles necessary for effective breathing and mucus clearance. This muscle weakness, combined with a reduced central ventilatory drive, makes it harder to clear the airways, contributing to a chronic cough.
Associated Conditions that Trigger Coughing
The persistent cough in hypothyroid patients is frequently a secondary symptom caused by conditions exacerbated by low thyroid function. Gastroesophageal Reflux Disease (GERD) and its variant, Laryngopharyngeal Reflux (LPR), are major non-cardiac causes of chronic cough strongly associated with hypothyroidism. Hypothyroidism can slow the digestive tract, potentially leading to increased stomach pressure and reduced efficiency of the esophageal sphincters that prevent reflux.
When stomach acid or non-acidic contents flow backward into the esophagus and reach the throat, it causes irritation and inflammation, even without typical heartburn symptoms. This “silent reflux” (LPR) is a known trigger for a chronic, dry cough and throat clearing. Obstructive Sleep Apnea (OSA) also affects many hypothyroid patients due to myxedema-related swelling and muscle weakness in the upper airway. OSA can lead to persistent mouth breathing and throat dryness overnight, often resulting in a morning cough or throat irritation upon waking.
Distinguishing the Cause and Finding Relief
Diagnosing a cough linked to hypothyroidism requires a systematic approach to rule out common respiratory causes like allergies, asthma, or infection. The initial step involves comprehensive blood testing to assess thyroid hormone levels, including Thyroid-Stimulating Hormone (TSH) and free T4. If these results confirm hypothyroidism, the primary treatment strategy begins with thyroid hormone replacement therapy, typically using levothyroxine.
Levothyroxine restores hormone balance, which can reverse myxedema-related swelling in the larynx and pharynx, often resolving the associated globus sensation and cough. Improvement may be gradual, taking several weeks or months as tissue swelling subsides and muscle function improves. If the cough persists despite normalized thyroid levels, the next step is investigating associated conditions, using specialized monitoring or endoscopy to diagnose GERD or LPR.
If an enlarged thyroid gland, or goiter, is physically compressing the trachea or laryngeal nerve, the cough may not respond fully to hormone replacement alone. An ultrasound may be used to evaluate the goiter size, and surgical intervention might be necessary to relieve pressure on the airway. Consulting a healthcare professional is necessary for proper diagnosis and to tailor a treatment plan addressing both the thyroid deficiency and any secondary conditions contributing to the chronic cough.