Bacterial Overgrowth and Irritable Bowel Syndrome (IBS) – What is the Hypothyroid/Levothyroxine Connection?

Hypothyroid victims on Levothyroxime have a 3 times relative risk to having bacterial overgrowth and the IBS connection that goes with it.

World J Gastroenterol. 2017 Feb 7;23(5):842-852. doi: 10.3748/wjg.v23.i5.842.
Levothyroxine therapy and impaired clearance are the strongest contributors to
small intestinal bacterial overgrowth: Results of a retrospective cohort study.
Brechmann T et al
http://www.wjgnet.com/1007-9327/full/v23/i5/842.htm

• 1809 case German study
• Connections found:
  – gastrectomy, OR = 3.5
  – PPI therapy OR = 1.4
  – impairment of intestinal clearance (any resecting gastric surgery OR = 2.6, any colonic resection OR = 1.9, stenosis OR = 3.4, gastroparesis OR = 3.4, neuropathy 2.2,
  – immunological factors (any drug-induced immunosuppression OR = 1.8)
  – altered thyroid gland metabolism (hypothyroidism OR = 2.6, levothyroxine therapy OR = 3.0)

Bacterial overgrowth is commonly associated with IBS.  They were at a loss to explain the levothryoxine connection.

Comment – does levothryoxine negatively effect the gut? Is it the autoimmune process that makes thyroid replacement necessary? Don’t know; but will consider that more in IBS patients on Levothyroxine…