Can ashwagandha suppress thyroid function?

Ashwagandha and Thyroid Function: Potential for Thyroid Suppression

Yes, ashwagandha can suppress thyroid function and potentially cause thyrotoxicosis in some individuals. While research shows mixed effects, several case reports document thyroid dysfunction following ashwagandha use.

Evidence of Ashwagandha's Effects on Thyroid Function

• Case reports have documented thyrotoxicosis in previously healthy individuals following ashwagandha supplementation, with symptoms resolving after discontinuation of the supplement 1, 2, 3
• A 32-year-old healthy woman developed thyrotoxicosis after increasing her dose of ashwagandha herbal extract, with laboratory confirmation of the condition and resolution of symptoms after discontinuation 1
• A 47-year-old previously healthy man developed painless thyroiditis with typical thyrotoxicosis symptoms after taking ashwagandha for two months, confirmed by thyroid ultrasonography and scintigraphy 2
• A 73-year-old female presented with supraventricular tachycardia and symptoms of hyperthyroidism with significantly low TSH levels after two years of using ashwagandha root extract as a self-administered treatment for hypothyroidism 3

Contradictory Evidence

• One small randomized controlled trial (n=50) found that ashwagandha root extract (600 mg daily) actually improved thyroid function in patients with subclinical hypothyroidism over an 8-week period, normalizing serum TSH, T3, and T4 levels compared to placebo 4
• A safety study in healthy volunteers found no statistically significant changes in thyroid hormonal profile after 8 weeks of ashwagandha supplementation (300 mg twice daily) 5

Thyroid Function and Regulation

• Thyroid function is primarily regulated by thyroid stimulating hormone (TSH) from the pituitary gland, which controls multiple aspects of thyroid hormone synthesis 6
• Adequate iodine intake (150 μg/day in adults) is essential for proper thyroid hormone synthesis, and deficiencies in iron and selenium can impair thyroid function 6
• TSH levels alone are not always a sensitive indicator of thyroid status, as concentrations are usually maintained within normal range despite frank iodine deficiency 6

Clinical Implications and Monitoring

• Thyroid dysfunction can manifest as hypothyroidism (insufficient thyroid hormone production) or hyperthyroidism (excess thyroid hormone production) 6
• The serum TSH test is the primary screening test for thyroid dysfunction, with multiple tests recommended over a 3-6 month interval to confirm or rule out abnormal findings 7
• Follow-up testing of serum T4 levels in persons with persistently abnormal TSH levels can differentiate between subclinical (normal T4 levels) and "overt" (abnormal T4 levels) thyroid dysfunction 7

Recommendations for Patients Taking Ashwagandha

• Individuals with pre-existing thyroid conditions should exercise caution when considering ashwagandha supplementation due to its potential effects on thyroid function 1, 2, 3
• Patients taking ashwagandha should be monitored for symptoms of thyroid dysfunction, including fatigue, weight changes, temperature sensitivity, and changes in heart rate 2, 3
• If symptoms of thyroid dysfunction develop while taking ashwagandha, discontinuation of the supplement is recommended, with monitoring for resolution of symptoms 1, 2
• Healthcare providers should include questions about herbal supplement use, including ashwagandha, when evaluating patients with unexplained thyroid dysfunction 1, 3

Potential Mechanisms

• While the exact mechanism by which ashwagandha affects thyroid function is not fully understood, animal studies have suggested that it can increase serum concentrations of thyroid hormones 1
• The bidirectional effect (both stimulating and suppressing thyroid function in different contexts) suggests complex interactions with the hypothalamic-pituitary-thyroid axis 4, 3

Given the documented cases of thyrotoxicosis associated with ashwagandha use and the potential serious consequences of thyroid dysfunction, caution is warranted when using this supplement, particularly in individuals with pre-existing thyroid conditions or those taking thyroid medications.