Related Experiment Videos
Thyroid status and hepatic thyroxine deiodinating activity under high-dose long-term nitrendipine
J Wieberneit1, C F Wolf, F S Keck
1Department of Internal Medicine I, Medical Clinic, University of Ulm, Germany.
Pharmacology & Toxicology
|April 1, 1992
Summary
High doses of oral nitrendipine in baboons induced a hypothyroid state, decreasing thyroxine and reverse triiodothyronine while increasing TSH. This was linked to enhanced hepatic 5-deiodination activity.
Area of Science:
- Endocrinology
- Pharmacology
- Toxicology
Background:
- The hypophyseal-thyroid axis regulates metabolism.
- Thyroid hormone metabolism involves deiodination.
- Nitrendipine is a calcium channel blocker with potential endocrine effects.
Purpose of the Study:
- To investigate the effects of high-dose oral nitrendipine on the hypophyseal-thyroid axis in baboons.
- To examine the impact of nitrendipine on peripheral thyroxine metabolism.
Main Methods:
- Baboons were administered high doses (320 mg/kg b.wt.) and lower doses (24 and 48 mg/kg b.wt.) of oral nitrendipine for three months.
- Measurements included serum thyroxine (T4), reverse triiodothyronine (rT3), triiodothyronine (T3), and thyroid-stimulating hormone (TSH).
- Hepatic 5'-deiodinating activity and Vmax were assessed.
Main Results:
- High-dose nitrendipine administration resulted in a hypothyroid state, characterized by decreased T4 and rT3, and elevated TSH.
- Serum T3 levels remained unchanged despite decreased T4.
- Concomitant increase in hepatic 5'-deiodinating activity (Vmax) was observed with high-dose nitrendipine.
Conclusions:
- High oral doses of nitrendipine disrupt the hypophyseal-thyroid axis in baboons, leading to hypothyroidism.
- Enhanced peripheral 5'-deiodination contributes to maintaining normal T3 levels despite low T4 concentrations.
- These findings highlight potential endocrine side effects of high-dose nitrendipine therapy.