What is the relationship between thyroid function and Low-Density Lipoprotein (LDL) cholesterol levels?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: March 24, 2025 • View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

Thyroid function has a significant impact on Low-Density Lipoprotein (LDL) cholesterol levels, with hypothyroidism typically raising LDL levels and hyperthyroidism lowering them. The relationship between thyroid function and LDL cholesterol is rooted in the role of thyroid hormones in regulating lipid metabolism. When thyroid hormone levels are low, as in hypothyroidism, the number of LDL receptors decreases, leading to reduced clearance of LDL from the bloodstream and consequently higher blood levels 1. On the other hand, hyperthyroidism is associated with increased metabolism and LDL clearance, resulting in lower LDL levels.

Key Considerations

  • Thyroid hormones affect plasma lipoprotein(a) levels, with hypothyroid patients having higher and hyperthyroid patients having lower concentrations 1.
  • Appropriate treatment of thyroid disorders can lead to changes in lipoprotein(a) levels towards those of euthyroid controls 1.
  • Conventional lipid-lowering drugs, including statins and fibrates, may have inconsistent effects on plasma lipoprotein(a) levels 1.
  • Nicotinic acid or derivatives can consistently reduce lipoprotein(a) by up to 35% by interfering with apo(a) transcription 1.

Clinical Implications

  • For patients with elevated LDL and thyroid dysfunction, optimizing thyroid function first is crucial before initiating specific lipid-lowering therapies, as correcting the thyroid disorder may substantially improve cholesterol levels without additional medication.
  • Regular monitoring of both thyroid function (TSH, free T4) and lipid profiles is recommended during treatment adjustments to ensure optimal management of both conditions.
  • Treatment of hypothyroidism with levothyroxine can lead to improvement in lipid profiles, with LDL levels frequently decreasing once thyroid function normalizes.

From the Research

Relationship Between Thyroid Function and LDL Cholesterol Levels

The relationship between thyroid function and Low-Density Lipoprotein (LDL) cholesterol levels is complex and has been investigated in several studies.

  • Thyroid hormones play a crucial role in lipid metabolism, and alterations in thyroid function can affect LDL cholesterol levels 2, 3, 4, 5.
  • Levothyroxine replacement therapy has been shown to decrease LDL cholesterol levels in patients with hypothyroidism, suggesting a beneficial effect on lipid profiles 2, 4, 5.
  • The mechanism by which thyroid hormones affect LDL cholesterol levels involves the stimulation of LDL-receptor expression and the conversion of cholesterol to bile acids 3.
  • Some studies have reported that levothyroxine therapy can reduce LDL cholesterol levels and improve clinical symptoms in patients with subclinical hypothyroidism 5.
  • However, other studies have found that levothyroxine monotherapy may not completely normalize systemic biological markers of thyroid hormone signaling, including serum LDL and total cholesterol levels 6.

Effects of Levothyroxine Therapy on LDL Cholesterol Levels

The effects of levothyroxine therapy on LDL cholesterol levels have been investigated in several studies.

  • A prospective study found that levothyroxine replacement therapy significantly reduced mean LDL cholesterol levels in patients with overt hypothyroidism 2.
  • Another study reported that levothyroxine therapy decreased LDL cholesterol levels and improved lipid profiles in patients with hypothyroidism 4.
  • A systematic review and meta-analysis found that levothyroxine-treated hypothyroid participants with normal serum TSH levels had higher serum LDL levels compared to controls 6.

Clinical Implications

The relationship between thyroid function and LDL cholesterol levels has important clinical implications.

  • Thyroid dysfunction can increase the risk of cardiovascular disease, and treatment of hypothyroidism with levothyroxine may help reduce this risk by improving lipid profiles 2, 3, 5.
  • Clinicians should be aware of the potential effects of levothyroxine therapy on LDL cholesterol levels and monitor patients accordingly 2, 6.
  • Further research is needed to fully understand the relationship between thyroid function and LDL cholesterol levels and to optimize treatment strategies for patients with hypothyroidism 6.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Related Questions

Will increasing levothyroxine (T4) by 25 micrograms (mcg) improve low-density lipoprotein (LDL) levels?
What is the next step in managing a patient with hypothyroidism on Synthroid (levothyroxine) 125 mcg who has a history of hyperlipidemia and reports improved symptoms?
What adjustments should be made to the treatment regimen of a 76-year-old female patient with increasing hypercholesterolemia and rising TSH levels while on atorvastatin and levothyroxine?
What is the treatment for a patient with hypothyroidism and hyperlipidemia?
Should a patient with subclinical hypothyroidism and hypercholesterolemia be treated with levothyroxine?
What is the possible differential diagnosis for a patient with disseminated follicular lesions, presenting with scaly plaques and pruritus, affecting the trunk, extremities, and palms, for 10 years?
What is the expected survival time of a hospice patient without nutrition or hydration?
What is the maximum dose of hyoscine (scopolamine) butylbromide?
What is the typical negative inspiratory pressure (NIP) or force in a normal healthy adult?
What is the purpose of a bubble study (Contryst Desk (Contryst Desk) - contrast ultrasound study) to diagnose patent (patent) right-to-left cardiac shunt or other cardiac abnormalities?
What are the guidelines for dose adjustment during Continuous Renal Replacement Therapy (CRRT) in patients with Impaired renal function?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question