Low Doses of Cholestyramine in the Treatment of Hyperthyroidism
Low Doses of Cholestyramine in the Treatment of Hyperthyroidism
The enterohepatic circulation of thyroid hormones is increased in thyrotoxicosis.Bile-salt
 sequestrants (ionic exchange resins) bind thyroid hormones in the intestine and thereby
 increase their fecal excretion. Based on these observations, the use of cholestyramine has
 been tried. The present study evaluates the effect of low doses of cholestyramine as an
 adjunctive therapy in the management of hyperthyroidism
The gastrointestinal tract has a role in thyroid physiology. Thyroid hormone is metabolized
 mainly in the liver, where it is conjugated to glucurunides and sulfates. These conjugation
 products are then excreted in the bile. Free hormones are released in the intestine and
 finally reabsorbed, completing the enterohepatic circulation of thyroid hormone. A very small
 portion of the daily production of thyroxin (T4) and triiodothyronine (T3), less than 10
 percent, is excreted in the stool (1-3). In people with normal thyroid function, this pathway
 of T4 and T3 recirculation contributes so little to hormone availability that patients who
 have gastrointestinal disease or are receiving drugs that decrease T4 absorption do not have
 abnormal thyroid function (4). However, the thyrotoxic states are characterized by an
 increased enterohepatic circulation of thyroid hormones, as well as an increased urinary and
 fecal excretion of both conjugated and free T4 (5,6).

 Cholestyramine, an ionic exchange resin sequesters T4 in the intestine and increases its
 fecal excretion. These phenomena were proven in hamsters in mid 1960s (7). Experimentally, it
 has been shown that 50 mg of cholestyramine can bind approximately 3000 μg of T4 (8) and
 therefore can enhance the clearance of thyroid hormones. Because of the increased
 enterohepatic circulation of thyroid hormones during hyperthyroidism, attempts have been made
 to sequester these hormones in the intestine using ionic exchange resins (9-13).
 Cholestyramine therapy has been studied in the treatment of thyrotoxicosis as an adjunctive
 therapy to thionamides, and has been found to decrease thyroid hormone levels rapidly. In
 several trials, cholestyramine in combination with methimazole (MMI) or propylthiouracil,
 caused a more rapid decline in thyroid hormone levels than standard therapy with thionamides
 alone (9-11,13). In all of these trials, cholestyramine was dosed at 4 grams orally two to
 four times a day.

 This study was conducted to examine the efficacy of combination therapy of lower doses of
 cholestyramine with MMI and propranolol for treating patients with Graves' hyperthyroidism.
Inclusion Criteria:

 -  Patients with newly diagnosed hyperthyroid Graves' disease

 Exclusion Criteria:

 -  If the patient had been treated previously

 -  diabetes, kidney, or liver disease