Hypothyroidism, or underactive thyroid, is a medical condition where the thyroid gland fails to produce enough hormones to keep the body's metabolism working properly. The condition is quite common—it affects more than 27 million adult Americans,1 mainly women over 40 years old and the elderly of both sexes. Up to 13 million Americans have undiagnosed hypothyroidism.2
Doctors typically prescribe a medication called levothyroxine, a synthetic form of thyroid hormone replacement. However, some people with hypothyroidism have difficulty tolerating or absorbing the traditional medication, in which case your doctor might consider prescribing a more "pure" levothyroxine formulation available in a gelatin capsule. It may offer advantages over traditional tablets, especially if you have certain gastrointestinal (GI) issues.
Diagnosis and Treatment
The broad range of hypothyroidism symptoms are similar to those of many other diseases and might include fatigue, forgetfulness, dry skin, coarse hair or hair loss, weight gain, cold intolerance, weakness, constipation, elevated cholesterol, muscle aches and depression. This combined with the fact that symptoms can vary with the severity of the thyroid hormone deficiency makes hypothyroidism an often overlooked diagnosis.
When your doctor tests your blood level of thyroid-stimulating hormone (TSH), a higher blood level signals a more underactive gland. But TSH levels can temporarily fluctuate with non-thyroid illness as well, and an elevated TSH value may be normal for people over 70 years old.3
Effective communication between you and your doctor is critical to the success of hypothyroidism treatment. Tell your doctor about your symptoms, medications and supplements you are taking, allergies, other medical conditions you have, and family history of disease. Also alert your doctor if you experience new symptoms or start taking a new medication or supplement. Both doctors and patients should keep an open mind in terms of what could be causing new symptoms.
In most cases, treatment of hypothyroidism is lifelong. After the initial treatment, your doctor will continue to monitor your progress and may adjust the dosage of levothyroxine to make sure it is right for you. To help get your TSH levels to the desired goal, it is extremely important to take your medication exactly as prescribed, consistently, usually early in the morning, at least one hour apart from food or other pills and with water (as opposed to orange juice or milk) which will allow for optimal absorption). Ideally, the same manufacturer should always be used.
The commonly prescribed treatment, levothyroxine tablets, is a synthetic version of a hormone called thyroxine, or T4, produced by the thyroid gland. But some people have erratic thyroid laboratory results with this treatment or find it difficult to tolerate. The excipients, or inactive ingredients, commonly found in levothyroxine medications can rarely cause allergic reactions or GI problems, the latter particularly if you have celiac disease or lactose intolerance.4
Traditional levothyroxine tablets contain a variety of excipient ingredients, such as food dyes, alcohol, magnesium stearate, povidone and talc that can cause allergic reactions. The Full Prescribing Information included with every levothyroxine prescription lists the ingredients.
Exposure to even minute quantities of allergy-triggering ingredients can cause a reaction in susceptible people. For example, an allergy to a drug's inactive ingredients can cause a rash or a GI reaction such as diarrhea by aggravating the underlying celiac disease or lactose intolerance.5 Often, people who experience these side effects simply stop taking their levothyroxine medicine, a common reason for undesirably high TSH levels and a return of thyroid disease symptoms. If you experience a reaction after taking the medication, consult with your doctor or pharmacist.
Celiac disease, which can occur at any age, is an autoimmune disorder of the GI tract triggered by consuming gluten (wheat, barley and rye). In adults, signs and symptoms vary and may include: unexplained iron-deficiency anemia, fatigue, weight loss, diarrhea, bloating, arthritis, bone loss or osteoporosis, depression, an itchy skin rash, and infertility. People with celiac disease are nearly four times more likely to develop an autoimmune thyroid condition, such as Hashimoto's disease, the most common cause of hypothyroidism. Between 1.5% and 6.7% of people with autoimmune thyroid disorder also have celiac disease. Celiac disease affects one in 133 healthy people to one in 22 people who have immediate relatives (parent, child or sibling) who have the disease.6 Because traditional levothyroxine medications contain gluten, and even minute amounts of gluten can affect the intestines of celiac patients, they can conceivably cause celiac symptoms to worsen.7
People with celiac disease may only have subtle symptoms, but they can still develop complications of the disease over time. Long-term complications include malnutrition, which can lead to anemia, osteoporosis, and miscarriage. Untreated celiac disease can lead to a higher risk for GI cancers. A study has shown untreated celiac disease causes malabsorption of levothyroxine; absorption may improve after celiac disease treatment.8 It is extremely important for celiac patients to avoid gluten.
Lactose is an inactive ingredient found in traditional levothyroxine medications. Lactose intolerance is the inability to digest lactose, a sugar found in milk and other dairy products. Many foods also contain lactose, including baked goods, cereals, salad dressings, mayonnaise, puddings and artificial sweeteners.
Between 30 and 50 million Americans are lactose intolerant.9 Common symptoms include abdominal discomfort or pain, nausea, vomiting, diarrhea, constipation and gas after consuming foods containing lactose. Lactose intolerance often produces digestive tract discomfort 30 minutes to two hours after consuming milk products.
The condition can be hard to diagnose, as many people occasionally suffer from symptoms similar to those produced by lactose intolerance. Other conditions, such as irritable bowel syndrome or celiac disease, can also produce similar symptoms. Diagnostic tests are available, but an easy way to tell if you have lactose intolerance is to see if your symptoms subside after eliminating lactose-containing products from your diet for a few weeks.
If you have lactose intolerance, even the small amount of lactose contained in pills, in cumulative combination with small amounts from food or medication, may be enough to cause discomfort.
Conditions Causing Poor Absorption of Traditional Levothyroxine Tablets
A landmark study in The New England Journal of Medicine showed that people with poor stomach acid production from various causes have lower absorption of the tablet form of levothyroxine.10 Others with conditions such as inflammatory bowel syndrome, Helicobacter pylori (H. pylori) gastritis, and atrophic gastritis typically cannot optimally absorb levothyroxine tablets and generally require a higher dose. A class of commonly prescribed drugs called proton pump inhibitors potently lower stomach acid production. Since these acid blocking drugs are often taken as needed or "off and on," this can cause a "moving target" for physicians and potentially cause problems in regulating thyroid hormone levels with traditional T4 tablets. Taking certain drugs or supplements (notably: iron or calcium supplements), some foods, and various conditions of the GI tract can also affect T4 absorption.
Another Option for Some Patients with Hypothyroidism
If you have one of the above conditions, your doctor may want to consider prescribing a newer form of levothyroxine available in a soft gelatin capsule. The medication consists of T4 and only three inactive ingredients: glycerin, gelatin, and water—far fewer than in traditional levothyroxine tablets. The capsules, which are bioequivalent to the leading levothyroxine tablets, are free of dyes, gluten, lactose, sugar, alcohol and other ingredients that can cause allergic reactions or worsening of your GI symptoms.
In a recent study, the capsules, in contrast to traditional levothyroxine tablets, showed constant dissolution regardless of stomach acidity, which should theoretically enable better control of hypothyroidism for people with gastric disorders.11 The gelatin capsules were recently noted in national guidelines on hypothyroidism.4 More research in this area is pending. If you have hypothyroidism but have difficulty tolerating your medication, particularly if you have an allergic reaction to the excipients or suffer from celiac disease, lactose intolerance, or a condition that affects gastric acidity, and your thyroid blood test results are erratic, the gelatin capsule form of levothyroxine is a good option to discuss with your doctor.
Peer Review by Grazia Aleppo, MD, FACE, FACP
Although I believe that subjects who have celiac disease may need to be on this type of preparation, it is also true that—to date, many patients have been tolerating levothyroxine, even in the presence of celiac disease or lactose intolerance.
1. Spinger G. Thyroid Disease—Why This Epidemic? Personal Health Connections, 2011. www.personalhealthconnections.com/2011/thyroid-disease-why-this-epidemic/. Accessed December 10, 2013.
2. Shomon M. Thyroid Disease Is Far More Widespread Than Originally Thought: 13 Million May Be at Risk and Undiagnosed. Colorado Thyroid Disease Prevalence Study. Updated August 12, 2013. http://www.thyroid-info.com/articles/thyroid-prevalence.htm. Accessed December 10, 2013.
3. Vadiveloo T, et al. Age- and Gender-Specific TSH Reference Intervals in People With No Obvious Thyroid Disease in Tayside, Scotland: The Thyroid Epidemiology, Audit, and Research Study (TEARS). J Clin Endocrinol Metab. 2013;98(3):1147.
4. Garber JR, Cobin RH, Gharib H, Hennessey JV, et al. Association Taskforce of Hypothyroidism in Adults. Clinical practice guidelines for hypothyroidism in adults: co-sponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association [published online ahead of print, 2012]. Endocrine Pract. 2012; doi:10.4158/EP12280.GL.
5. Swerlick R, Campbell CF. Medication Dyes as a Source of Drug Allergy. J Drugs Dermatol. 2013;12(1):99-102.
6. Celiac Disease Facts and Figures. The University of Chicago Celiac Disease Center. http://www.uchospitals.edu/pdf/uch_007937.pdf. Accessed December 10, 2013.
7. Catassi C, Fabiani E, Iacono G, D'Agate C, et al. A prospective, double-blind, placebo-controlled trial to establish a safe gluten threshold for patients with celiac disease. Am J Clin Nutr. 2007;85:160-6.
8. Collins D, Wilcox R, Zubarik R. Celiac disease and hypothyroidism. Am J Med. 2012;125(3):278-82.
9. Prevalence, Age and Genetic of Lactose Intolerance: Data from NIDDK. National Institute of Diabetes and Digestive and Kidney Diseases. http://www.foodreactions.org/intolerance/lactose/prevalence.html. Accessed December 10, 2013.
10. Centanni M, Gargano L, Canettieri G, Viceconti N, et al. Thyroxine in Goiter, Helicobacter pylori Infection, and Chronic Gastritis. N Engl J Med. 2006;354:1787-1795.
11. Virili C, Santaguida MG, Cellini M, Del Duca SC, et al. Pilot Study With Softgel Thyroxine Preparation in the Treatment of Patients With T4 Malabsorption Due to Gastric Disorders. Data presented at ENDO 2013, Endocrine Society 95th Annual Meeting. Abstract. https://endo.confex.com/endo/2013endo/webprogram/Paper6139.html. Accessed December 10, 2013.