Black Cohosh Effects on Liver, TSH, and Cholesterol
Black cohosh has documented hepatotoxic potential requiring monitoring of liver function, but there is no established evidence linking it to TSH or cholesterol level alterations.
Hepatotoxicity Risk
Black cohosh carries a real, though rare, risk of liver injury that can range from mild enzyme elevations to severe hepatotoxicity requiring transplantation.
Evidence of Liver Toxicity
- Several case reports document severe hepatotoxicity associated with black cohosh use, including cases requiring liver transplantation 1, 2, 3
- A 60-year-old woman developed subacute liver failure after taking black cohosh, confirmed by liver biopsy, and required liver transplantation 1
- A 50-year-old woman presented with cholestatic liver injury (elevated bilirubin and alkaline phosphatase) that resolved 6 months after discontinuing black cohosh 2
- A 44-year-old woman developed subacute liver injury within one month of black cohosh use, demonstrated on CT scan and liver biopsy 3
Causality Assessment Challenges
- The causality link between black cohosh and hepatotoxicity remains controversial due to poor documentation in most reported cases 4, 5
- In systematic reviews of 69 cases, causality was excluded, unlikely, or unassessable in 68 of 69 patients using structured CIOMS assessment methods 4
- Common confounding variables include: unidentified product brands, herbal mixtures with multiple ingredients, concomitant medications, pre-existing liver disease, and missing temporal associations 4, 5
Clinical Recommendation for Liver Monitoring
Patients taking black cohosh should have baseline liver function tests and periodic monitoring, especially if other hepatotoxic risk factors are present 1, 2, 3. The United States Pharmacopeia recommends cautionary warnings about hepatotoxicity be labeled on black cohosh products 3.
TSH (Thyroid Function) Effects
There is no evidence in the provided literature that black cohosh affects thyroid-stimulating hormone levels. The guideline references to TSH monitoring relate to other medications (ethionamide for tuberculosis treatment and interferon therapy for hepatitis C), not to black cohosh 6.
Important Distinction
- TSH monitoring is recommended for drugs like ethionamide (which can cause hypothyroidism) at baseline and monthly intervals 6
- Interferon therapy can cause thyroid dysfunction in 15-20% of patients, requiring TSH monitoring at 2-4 month intervals 6
- These monitoring recommendations do not apply to black cohosh, which has no documented thyroid effects
Cholesterol Effects
Black cohosh has no established effects on cholesterol levels based on available evidence. The guideline discussions of cholesterol management involve bile acid sequestrants, statins, and other lipid-lowering therapies, not herbal supplements like black cohosh 6.
Clinical Efficacy Concerns
Beyond safety considerations, black cohosh lacks robust evidence for efficacy in treating menopausal symptoms 6. A randomized trial comparing black cohosh, multibotanicals with black cohosh or soy, hormone therapy, or placebo in healthy menopausal women found that black cohosh provided no benefit, and only estrogen was effective 6.
Key Clinical Pitfalls
- Patients often fail to disclose herbal supplement use unless specifically asked 3
- Always obtain a complete supplement history when evaluating unexplained liver enzyme elevations
- The perception that herbal preparations are without adverse effects is dangerous and incorrect 1
- Product variability (unknown brands, dosages, and potential adulterants) complicates risk assessment 4, 5