Reasons for High TSH Blood Levels

Thyroid Stimulating Hormone (TSH) is a hormone produced by the body to alert the thyroid gland to produce more T3 and T4 thyroid hormones. When the thyroid is not producing enough hormones, called hypothyroidism, TSH will rise in an effort to increase production. Many factors can cause TSH to increase above the normal range of 0.3 to 3 mlU/L.

Medication Timing

• Hormone medications should be taken at the same time every day and on an empty stomach. The presence of food in the gastrointestinal tract can delay or reduce the hormone's absorption rate, which can cause TSH to rise. Hormone replacement may also need to be taken separately from other drugs, particularly antidepressants and cholesterol-lowering medications.

Multivitamin or Supplement Use

• Calcium and iron can both interfere with the absorption of thyroid hormone medications and should be taken at least two to four hours separately from the drug. Some herbal supplements may also interfere with thyroid replacement therapy.

Increased Estrogen Levels

• Hormonal replacement therapy for menopause treatment, birth control pills and pregnancy all result in a rise in the hormone estrogen, which can interfere with the production of the thyroid gland and impact TSH levels. Overconsumption of soy foods may also be a problem with patients who have an autoimmune thyroid disease, as the isoflavones in soy act similarly to estrogen in the body.

Change of Season or Acute Illness

• TSH can naturally rise during colder months, particularly in older patients. Some physicians may adjust for this by changing dosage levels of the medication. Stress and illness can also affect TSH levels temporarily.

High Dietary Fiber Intake

• Fiber affects the speed of digestion and absorption in the stomach, which can reduce the bioavailability of hormone medications, causing TSH to rise. It is not necessary to avoid fiber. Have thyroid levels tested six to eight weeks after the diet change, and then remain consistent with fiber intake.

Goitrogenic Foods

• Certain foods may enlarge the thyroid, called a goitrogenic effect, which interferes with its ability to produce thyroid hormone. These include brussels sprouts, rutabaga, turnips, radishes, cauliflower, cabbage and kale. Cooking may destroy most of the goitrogenic compounds in the foods.