High serum bile acids cause hyperthyroidism and goiter.
OBJECTIVE
In the duodenal content reflux model of rats, we noted an elevation of serum bile acid and swelling of the thyroid gland. This study was designed to elucidate whether bile acids (BAs) also enhance thyroid function.


METHODS
In varying lengths of period after esophago-jejunostomy without gastrectomy, which causes duodenal content reflux, rats were sacrificed and blood samples were taken from the heart for analyses of BAs and triiodothyronine (T3), thyroxine (T4), free T3 (fT3), free T4 (fT4), and thyroid-stimulating hormone (TSH) in the serum.


RESULTS
Macroscopically, at 10 and 30 weeks after operation, thyroid glands in the reflux model showed a symmetric enlargement because of the presence of diffuse hypertrophy of the thyroid follicular epithelium. At both time points, no significant differences were detected in T3, T4, fT3, and fT4 levels between the reflux model and the control group, whereas, at 10 weeks after operation, the animals with the reflux showed significantly lower serum TSH levels and greater thyroid weight than those in the control group. An inverse correlation between serum BAs and TSH levels was noted in the reflux model but not in the control group. Microscopically, thyroid follicles were greater in size and number, with paler colloids in the reflux model than the control group.


CONCLUSIONS
The present results suggest that high serum BAs cause hyperplasia of the thyroid follicles and the reduction of TSH. The effects of BAs on thyroid hormones, thus, include the induction of overall hyperthyroidism. Therefore, the strict monitoring of serum TSH levels is of vital importance if BAs are used for the treatment of obesity.
Mukaisho
Ken-Ichi
K
Department of Pathology, Shiga University of Medical Science, Ohtsu, Shiga, Japan.
Araki
Yoshio
Y
Sugihara
Hiroyuki
H
Tanaka
Hiroyuki
H
Chen
Kuan-Hao
KH
Hattori
Takanori
T
D000818:Animals; D001647:Bile Acids and Salts / Q000097:blood*; D006042:Goiter / Q000209:etiology*; D006980:Hyperthyroidism / Q000209:etiology*; D008297:Male; D009929:Organ Size; D051381:Rats; D017208:Rats, Wistar; D013963:Thyroid Hormones / Q000097:blood
D001647:Bile Acids and Salts; D013963:Thyroid Hormones