For many years, hypothyroidism frequently has been associated with a variety of gastrointestinal manifestations, including constipation, distention, flatulence, ileus, atrophic gastritis, and atony and dilatation of the esophagus, stomach, small intestine, colon, and gallbladder. The occasional occurrence of a potentially life-threatening extension of the decreased gastrointestinal motility of hypothyroidism—myxedema megacolon—must be reemphasized.
Megacolon is characterized by a massive distention of the colon and is usually secondary to the absence of submucous (Meissner's) and myenteric (Auerbach's) plexuses in the distal colon. However, it may also arise secondary to a variety of systemic diseases, including scleroderma, dermatomyositis, polymyositis, amyloidosis, myotonic dystrophy, diabetes mellitus, and Chagas' disease, and from drugs, such as phenothiazines, tricyclic antidepressants, and antiparkinsonian agents.1 Reports of myxedema megacolon have appeared in medical literature over the last several decades.2-11 It is difficult to determine the incidence of this unusual complication, but in a review by Watanakunakorn et al
Solano FX, Starling RC, Levey GS. Myxedema Megacolon. Arch Intern Med. 1985;145(2):231. doi:10.1001/archinte.1985.00360020051007