Evaluation of the Effects of Clomipramine on Canine Thyroid Function Tests
Article first published online: 28 JUN 2008
Journal of Veterinary Internal Medicine
Volume 17, Issue 1, pages 44–49, January 2003
How to Cite
Gulikers, K. P. and Panciera, D. L. (2003), Evaluation of the Effects of Clomipramine on Canine Thyroid Function Tests. Journal of Veterinary Internal Medicine, 17: 44–49. doi: 10.1111/j.1939-1676.2003.tb01322.x
- Issue published online: 28 JUN 2008
- Article first published online: 28 JUN 2008
- Revised June 17, 2002: Accepted August 14, 2002.
- Tricyclic antidepressant
To evaluate the effect of long-term clomipramine administration on the hypothalamic-pituitary-thyroid axis in healthy dogs, 14 healthy adult dogs were enrolled in a prospective study. Clomipramine (3 mg/kg PO q12h) was administered to all dogs beginning on day 0, and continued for 112 days. Serum total thyroxine (T4), free thyroxine (fT4), 3,5,3'-triiodothyronine (T3), 3,3',5'-triiodothyronine (reverse T3; rT3), and thyroid-stimulating hormone (TSH) were measured on days 0, 7, 28, 42, 56, and 112. Thyrotropin-releasing hormone (TRH) response tests were performed concurrently. Significant decreases were noted in serum T4, fT4, and rT3 concentrations beginning on day 28 through the end of the study period. The lowest mean (ÆM) concentrations of T4 (26 ± 1.2 to 17 ± 0.5 nmol/L) and rT3 (1.21 ± 0.13 to 0.83 ± 0.08 nmol/L) occurred at day 112, whereas the lowest mean fT4 (29 ± 2.4 to 18 ± 1.7 pmol/L) was found on day 56 of clomipramine treatment. The effect of treatment over time on serum T3 concentration also was significant, but the deviation in T3 from baseline was variable. No significant effect of clomipramine treatment was noted on either pre- or post-TRH TSH concentrations. The 35 and 38% decreases in serum T4 and fT4 concentrations, respectively, during clomipramine administration may lead to a misdiagnosis of hypothyroidism. Although no evidence of hypothyroidism was noted in this study population, subclinical hypothyroidism may have occurred. A longer duration of treatment might further suppress thyroid function, and concurrent illness or other drug administration might exacerbate clomipramine's effects.