The thyroid gland is a small butterfly-shaped gland in the neck, just in front of the windpipe (trachea). One of its main functions is to produce hormones that help regulate the body's metabolism (the process that turns food into energy). These hormones are called triiodothyronine (T3) and thyroxine (T4). Many of the body's functions slow down when the thyroid doesn't produce enough of these hormones.
Esophageal spasm is a disorder of the rhythmic waves of muscular contractions (peristalsis) of the esophagus. The cause of this disorder is not known. Symptoms include chest pain and difficulty swallowing.
Some people have symptoms that combine those of achalasia (a disorder in which the rhythmic contractions of the esophagus are greatly decreased) and esophageal spasm because, in both disorders, the lower esophageal sphincter does not open properly. One such combination of symptoms has been called vigorous achalasia.