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Effect of ritodrine on thyroid hormone concentrations
P P Menheere1, G G Essed, J P Sels
1Department of Clinical Chemistry, University Hospital Maastricht, The Netherlands.
Summary
Ritodrine treatment in pregnant women temporarily increased triiodothyronine (T3) levels by stimulating deiodinase activity. This effect on thyroid hormones is temporary and may contribute to ritodrine
Area of Science:
- Endocrinology
- Pharmacology
- Obstetrics
Background:
- Ritodrine is a beta-2-sympathomimetic agent used for tocolysis.
- Propranolol, a beta-blocker, decreases T3 levels, suggesting a role for adrenergic stimulation in thyroid hormone regulation.
Purpose of the Study:
- To investigate the effect of ritodrine on thyroid hormone status in pregnant women.
- To test the hypothesis that adrenergic stimulation by ritodrine increases T3 levels.
Main Methods:
- A longitudinal clinical study involving 17 pregnant women treated with ritodrine.
- Assessment of serum thyroid hormone (T3, T4) and TSH concentrations before, during, and after ritodrine treatment.
Main Results:
- A significant, temporary increase in serum T3 concentrations was observed 24-48 hours after initiating ritodrine.
- T3 levels returned to baseline within one week of treatment and decreased after discontinuation.
- No significant changes in T4 or TSH levels were detected, indicating no impact on the pituitary-thyroid axis.
Conclusions:
- Ritodrine treatment stimulates type I deiodinase, leading to transient increases in T3.
- These beta-2-mimetic induced T3 variations may partially explain ritodrine's cardiac side effects.
- Caution is advised when using ritodrine in patients with hyperthyroidism.