23rd May 2025
Drugs and thyroid function
Lots of medications can affect thyroid gland function either through acting centrally on the hypothalamic-pituitary-thyroid axis or via acting directly on the thyroid gland. Some of these medications are shown in Table 7:
| Medication |
Type of thyroid dysfunction noted |
Any required monitoring |
| Amiodarone |
- Amiodarone has a high iodine content. Abnormalities in the form of hypo or hyperfunction of the gland are noted.
- Wolff-Chaikoff effect occurs where acute inhibition of TPO leads to inhibition of thyroid hormone synthesis.
- Sometimes Iodine excess contributes to thyrotoxicosis (Jod-Basedow phenomenon)
- AIH (amiodarone induced hypothyroidism) is noted in areas with high iodine intake.
- AIT (amiodarone induced thyrotoxicosis) occurs more frequently in regions with low iodine intake.
|
- TFTs should be monitored prior to initiating amiodarone and every 6 months.
|
| Iodine containing drugs used in CT imaging and cholecystography |
- Same phenomena described with amiodarone can occur. Hence, a hypo or hyperfunction of the gland can occur.
- These phenomena are particularly expressed in patients with pre-existing thyroid disorder.
|
|
| Lithium |
- Causes goitre and hypothyroidism picture by reducing thyroxine release via colloid pinocytosis inhibition.
- Lithium is noted to cause painless thyroiditis.
|
- Thyroid function testing before treatment initiation and every 6 months during treatment is recommended.
- More regular TFTs monitor is required in impaired thyroid function conditions.
|
Table 7: Medications and their effect on thyroid gland function