At first glance, there may seem to be no connection between thyroid disease and lactose intolerance. Thyroid disease is an immune system disorder; the body mistakenly recognizes a gland or tissue such as the thyroid as an "enemy" and attacks, either destroying the gland or causing it to malfunction. Lactose intolerance is an intolerance to milk and milk products that results from an inability to digest milk sugar. There is no indication that one condition causes the other, but there are some links between them.
Thyroid problems include low production of thyroid hormones – called hypothyroidism -- as well as thyroid nodules, thyroid cancer, goiter – an enlarged thyroid gland -- and production of too much thyroid hormone, which is called hyperthyroidism or Grave's disease. Thyroid disorders tend to develop slowly, may be difficult to diagnose as symptoms can be vague at first and are more likely to affect women than men. Hypothyroidism and Grave's disease have both been linked to lactose intolerance.
Lactose intolerance or lactase deficiency is an uncomfortable but not dangerous condition in which your body does not produce the enzyme needed to digest the milk sugar lactose. When lactase enzymes are low or absent, your body is unable to break down lactose into the simple sugars that are absorbed into your bloodstream. The unprocessed food moves into the colon where it causes gas, bloating and diarrhea. Lactose intolerance can be a genetic condition, the result of an illness or injury or simply part of the aging process.
Lactose Intolerance and Thyroid Medication
Lactose intolerance may interfere with your ability to take thyroid medication, because some thyroid preparations contain lactose. In a case study published in the 2003 "Endocrine Abstracts," researchers described a woman who was diagnosed with hypothyroidism or low thyroid. Her physician had appropriately prescribed a medication called thyroxine, but she stopped taking it because she developed severe abdominal bloating. She was diagnosed as being lactose intolerant and had to be changed to a different form of thyroid medication.
Lactose Intolerance and Resistance to Treatment
In another case reported in the 2006 "Thyroid," a patient was able to take the medication but it did not resolve her symptoms. The patient's lactose intolerance prevented her from absorbing the medication levothyroxine, and she continued to have thyroid disease symptoms even though she was being appropriately treated. Resistance to treatment is unusual, and eventually, the patient was tested for lactose intolerance and found to have the disease.
Grave's Disease and Lactose intolerance
Grave's disease, the condition in which the body produces too much thyroid hormone, was found to be linked to lactose intolerance in a study published in the June 1991 "Clinical and Investigative Medicine." Of 10 patients who were diagnosed with Grave's disease, nine also had lactose intolerance. When the Grave's disease was treated, seven of the 10 patients underwent studies to evaluate their lactose intolerance symptoms. Three patients no longer experienced problems with lactose absorption, and symptoms improved in two others.
- “Endocrine Abstracts”; Profound Hypothyroidism in a Patient With Lactose Intolerance; D Kapoor, et al.; 2003
- “Thyroid”; Lactose Intolerance Revealed by Severe Resistance to Treatment With Levothyroxine; M. Munoz-Torres, et al.; November 2006
- “Clinical and Investigative Medicine”; Reversible Lactose Malabsorption and Intolerance in Graves' Disease; A. Szilagyi, et al.; June 1991