Thyroid Patients, Be Aware of Biotin

Darius Schneider, MD, PhD

You’ve just had your thyroid hormone levels tested by your endocrinologist, and despite following your medication plan faithfully, your blood results come back puzzling. Your endocrinologist calls you with a series of questions, one being: “Are you taking any biotin-containing supplement?” You go to your medicine cabinet, examine the contents... and, eureka, you are indeed.

The test results had nothing to do with your thyroid, but rather, the biotin was interfering with your tests.

So, what is biotin?

Biotin is a readily available supplement that is part of the B complex group of vitamins. It is sold over the counter under a variety of names, including vitamin B7, vitamin H and coenzyme R, and sometimes may be an unnamed supplement advertised as an aid to improve hair and nail health.

The discovery of biotin occurred in response to research conducted in 1927 that investigated the cause of what was then called “egg white injury,” a vitamin-deficiency disease observed chiefly in animals that is induced by feeding upon an excess of raw egg whites.

Experiments done in 1942 demonstrated that when a biotin deficiency was induced in a group of healthy human volunteers, they developed skin changes, depression and muscle pain – side effects which were all reversible after the volunteers were given biotin.

Until the early 1970s, a biotin deficiency was thought to be impossible, because gut bacteria are able to produce the substance. However, people who have been on intravenous nutrition, anti-seizure medication, or certain antibiotics for a long period of time, as well as people with conditions like Crohn’s disease (a chronic inflammatory bowel disease that affects the lining of the digestive tract) – all of which can compromise your body’s ability to absorb nutrients from the gut – can develop biotin deficiency. Severe biotin deficiency can also be seen after excessive intake of the raw egg protein avidin, which is a biotin antagonist (a substance that interferes with or inhibits the physiological action of another).

What is its function?

Biotin is a component of enzymes involved in the breakdown of amino acids, the building blocks of protein, or the formation of long-chain fatty acids, the building blocks of fat. Biotin plays an important role in the formation of carbohydrates from non-sugars such as fats and proteins, thus helping the body to maintain normal blood glucose (blood sugar).

Biotin also plays a role in the growth and maintenance of nerve tissue. In cells of hair roots and of nails (so-called keratinocytes), biotin facilitates the formation of keratin, the building block of both hair and nails. Thus, higher concentrations of biotin can lead to the visible effect of smoother skin and healthier hair and nails. In contrast, biotin deficiency can lead to skin inflammation with redness and scaling, dry, cracking skin, hair loss, and a swollen and painful tongue. The complete absence of biotin causes a severe form of skin condition seborrheic dermatitis called Leiner's disease.

Recently, there has been some evidence that biotin may improve blood glucose levels, as well as symptoms of peripheral neuropathy (nerve disease) in people with diabetes. However, the research conducted thus far is inconclusive.

Recently, there has been some evidence that biotin may improve blood glucose levels, as well as symptoms of peripheral neuropathy (nerve disease) in people with diabetes. However, the research conducted thus far is inconclusive.

Where to find biotin naturally

Besides being found in many supplements, biotin is available in small amounts in brewer's yeast, egg yolk and sardines; nuts (almonds, peanuts, pecans, walnuts) and nut butters; soybeans, beans and black-eyed peas; whole grains; cauliflower; bananas; and mushrooms. In foods, it is bound to proteins. In order to be absorbed in the human gut, biotin has to be chemically separated from these proteins by an intestinal enzyme called biotinase, which is made by some bacteria in the human intestinal system.

In what way does biotin alter thyroid testing?

Recently, children with inherited metabolic diseases receiving high doses of biotin were found to have elevated levels of thyroid hormones and thyroid antibodies. These results resembled Graves’ disease, an autoimmune condition in which thyroid antibodies stimulate the thyroid gland to produce too much thyroid hormone, resulting in hyperthyroidism. However, the children did not have the typical symptoms of hyperthyroidism: they did not have a fast heart rate, restlessness, or show developmental delays. Further analyses revealed that biotin interferes with the most commonly used thyroid hormone test systems, mimicking lab results seen in Graves’disease.

Additional analyses have shown that biotin’s interference with lab tests can also result in a low thyroid hormone level reading, depending on which lab testing system is being used. After stopping biotin, interference with laboratory tests has been reported to disappear within eight hours, although other researchers have reported it might take 24 to 48 hours for some of the more typical tests that might be ordered, and up to seven days for some antibody tests.

What’s the solution?

The normal daily recommended intake for biotin in adolescents and adults is 30 to 100 micrograms. A daily intake of 30 micrograms is the amount contained in a multivitamin such as Centrum® Silver. Higher biotin intake is recommended for those who have high alcohol or nicotine consumption or persistent diarrhea, those who are undergoing treatment with antibiotics, people in high-stress situations, and performance athletes. Since biotin plays an important role in the formation and development of an embryo, it is also a critical nutrient during pregnancy.

However, milligrams of biotin intake (there are a thousand micrograms in a milligram) may interfere with thyroid testing. So be sure to tell your health team what supplements you are taking or, better yet, bring those supplements in for your next appointment.