Medications That Decrease Thyroid-Stimulating Hormone (TSH)
Several medications can decrease TSH levels, with levothyroxine being the most commonly used medication specifically designed for this purpose. When administered at appropriate doses, levothyroxine suppresses TSH through negative feedback on the pituitary gland 1.
Medications That Intentionally Decrease TSH
1. Thyroid Hormone Preparations
Levothyroxine (T4): The primary medication used to decrease TSH levels
- Mechanism: Provides exogenous thyroid hormone, creating negative feedback on the pituitary
- Dosing: Typically 1.6 mcg/kg/day in adults under 70 without cardiac disease 1
- Lower doses (25-50 mcg/day) recommended for elderly patients or those with cardiac conditions 1
- Used therapeutically for TSH suppression in thyroid cancer management 2
Liothyronine (T3): Less commonly used but more potent at suppressing TSH
- Often used in combination with levothyroxine in some treatment protocols
2. TSH Suppression Therapy
- Used primarily in thyroid cancer management
- Target TSH levels vary based on risk stratification:
Medications That Decrease TSH as a Side Effect
1. Glucocorticoids
- High-dose glucocorticoids (e.g., dexamethasone ≥4 mg/day) 4
- Mechanism: Decrease TBG production and inhibit TSH secretion
- Effect: Decrease T3 levels by approximately 30% with minimal change in T4 4
2. Dopamine Agonists
- Medications like bromocriptine and cabergoline
- Mechanism: Inhibit TSH secretion from the pituitary
3. Bile Acid Sequestrants
- Colesevelam, cholestyramine, colestipol
- Mechanism: May increase TSH in patients on thyroid hormone replacement by decreasing absorption 3, 4
- Post-marketing reports with colesevelam include increased TSH in patients receiving thyroid hormone replacement therapy 3
4. Other Medications That Affect Thyroid Function
Medications Affecting T4 Absorption
- Proton pump inhibitors
- Sucralfate
- Antacids (aluminum & magnesium hydroxides)
- Phosphate binders (calcium carbonate, ferrous sulfate)
- Orlistat 4
Medications Altering Thyroid Hormone Transport
- Estrogens (oral)
- Tamoxifen
- Androgens/anabolic steroids
- Salicylates (>2 g/day)
- Furosemide (>80 mg IV)
- Carbamazepine 4
Medications Altering Hepatic Metabolism
- Phenobarbital
- Rifampin
- Phenytoin 4
Medications Decreasing T4 to T3 Conversion
- Beta-blockers (propranolol >160 mg/day)
- Amiodarone 4
Clinical Considerations
Monitoring TSH Suppression
- Check thyroid function (TSH and free T4) 4-6 weeks after starting therapy 1
- Adjust dose to maintain TSH within target range based on clinical context
- Overtreatment with levothyroxine can increase risk of:
Age-Related Considerations
- Older patients require lower doses of levothyroxine to achieve the same TSH suppression 5
- Men over 60 years show greater age-related decrease in requirements than women 5
- Target TSH range for elderly is 1.0-4.0 mIU/L to avoid overtreatment 1
Common Pitfalls
Not accounting for drug interactions that affect levothyroxine absorption
- Administer levothyroxine at least 4 hours apart from bile acid sequestrants 4
- Take on empty stomach, separate from medications that affect absorption
Excessive TSH suppression
- Can lead to iatrogenic hyperthyroidism with symptoms including tachycardia, tremor, and weight loss
- Increases risk of osteoporosis and cardiac arrhythmias, especially in elderly 6
Failure to adjust dosing based on clinical context
- Patients with thyroid cancer require higher doses (2.11 μg/kg/day) than those with primary hypothyroidism (1.63 μg/kg/day) to achieve the same TSH level 7
Not recognizing transient hypothyroidism
When using medications to decrease TSH, careful monitoring and dose adjustment are essential to achieve the desired therapeutic effect while minimizing adverse consequences.