Can thyroid medicines be taken with statins and other medicines that treat high cholesterol?

The presence of hypothyroidism generally causes an increase in total and low density-lipoprotein cholesterol levels (LDL-C) while thyrotoxicosis tends to cause a net lowering of cholesterol levels.¹ Treatment for hypothyroidism with levothyroxine (L-thyroxine) often results in lowering of those cholesterol levels.^1,2

In most cases, medications that are prescribed specifically to lower LDL-C, like statins and non-statin medications, are safe to take with L-thyroxine.^3–12 Lovastatin, a statin, is listed as one of many medications that can affect thyroid hormone levels, but no specific warnings or contraindications are given. Manufacturer’s prescribing information for lovastatin recommends that secondary causes of dyslipidemia (including hypothyroidism) be considered prior to initiating therapy with lovastatin.⁶

Bile acid sequestrants, like cholestyramine or colestipol, may reduce the effectiveness of L-thyroxine.¹³ The manufacturer’s package insert for L-thyroxine recommends that if both of these types of medications are needed, they should be taken at least four hours apart.¹⁴

Concomitant use of lipid-lowering medications and L-thyroxine is not contraindicated and may be advised to lower cardiovascular risk, but it is important to consider a potential increased risk of side effects. Neuromuscular symptoms are common (up to 80%) in people with hypothyroidism. Untreated hypothyroidism is associated with many systemic and neurologic manifestations, including myopathy.¹⁵ Statins represent the most common drug class associated with myopathy. There have been numerous reports of an increased incidence of muscle-related symptoms among people with unrecognized hypothyroidism when initiating statin therapy.^15–17  The increased risk may or may not be related to the use of the statins and is likely to be impacted somewhat by the presence of the thyroid dysfunction. The 2018 American Heart Association/American College of Cardiology Guidelines for the Management of Blood Cholesterol strongly recommend that a clinician-patient discussion take place when initiating statin therapy which considers predisposing factors for statin-associated side effects.¹⁸ Individuals with known thyroid disease considering initiation of statin therapy can benefit from an understanding of signs and symptoms related to their thyroid function as well as the side-effect profile of potential lipid-lowering therapy.

^References

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2. Mihailescu D V, Vora A, Mazzone T. Lipid effects of endocrine medications. Curr Atheroscler Rep 2011; 13 : 88-94.
3. Rosuvastatin [package insert]. Wilmington DE: AstraZeneca Pharmaceticals; 2010.
4. Atorvastatin [package insert]. Dublin Ireland: Pfizer Parke-Davis;2009.
5. Simvastatin [package insert]. Cramlington UK: Merck, Sharpe & Dohne, LTD; 2010.
6. Lovastatin [package insert]. Morgantown WV: Mylan Pharmaceuticals.
7. Fluvastatin [package insert]. East Hanover NJ: Novartis Pharmaceuticals; 2012.
8. Pitavastatin [package insert]. Tokyo, Japan: Kowa Pharmaceuticals; 2012.
9. Pravastatin[package insert]. Princeton, NJ: Bristol Myers Squib.
10. Ezetimibe [package insert]. Whitehouse Station , NJ: Merck & Co, Inc; 2007.
11. Arilocumab [package insert]. Bridgewater, NJ: sanofi-aventis US, LLC; 2017.
12. Evololumab [package insert]. Thousand Oaks, CA: Amgen; 2017.
13. Cholestyramine [package insert]. Pointe-Claire, Quebec: Odan Laboratorie; 2016.
14. Levo-thyroxine [package insert]. Caguas, Puerto Rico: Neolpharma, Inc; 2017,
15. Katzberg HD, Kassardjian CD. Toxic and endocrine myopathies. Continuum 2016; 22 (6): 1815-1828.
16. Ramkumar S, Raghunath A, Raghunath S. Statin therapy : review of safety and potential side effects. Acta Cardiol Sin 2016; 32 : 631-639.
17. Robison CD, Bair TL, Horne BD, et al. Hypothyroidism as a risk factor for statin intolerance. J Clin Lipidol 2014; 8 (4): 401-407.
18. Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the management of blood cholesterol. J Am Coll Cardiol 2018.