a bottle of Synthroid (Levothyroxine) 50 mcg, take Synthroid, thyroid and cholesterol

Low thyroid function is extremely common. In fact, levothyroxine, the hormone used to treat an underactive thyroid gland, is the most frequently prescribed medication in the US. Many people are aware that a person with low levels of circulating thyroid hormone may feel fatigued and weak. He may be plagued with dry skin and constipation. She might notice brittle nails and excessive menstrual bleeding. But is there a connection between thyroid and cholesterol levels? One reader is trying to track that down.

Are Thyroid and Cholesterol Levels Linked?

Q. I was recently diagnosed with low thyroid function and am taking Synthroid (.025 mg per day) to regulate it. My cholesterol level has been increasing even though, at age 51, I am the same weight as I was in college, exercise regularly and watch my diet to minimize fat consumption–all the right stuff.

A consulting physician said that there is a relationship between low thyroid function and high cholesterol, but I have been unable to find any other documentation of this. Is this a recognized fact? Does balancing the thyroid really impact the cholesterol level?

A. Scientists have found clear evidence that mild hypothyroidism is linked to higher levels of cholesterol (Frontiers in Endocrinology, Sep. 3, 2018). In one year-long study, people with untreated subclinical hypothyroidism had significantly higher LDL cholesterol than those taking levothyroxine (Endocrine Practice, July-Aug. 2008). Moreover, a review of clinical trials confirmed that slightly hypothyroid people who took levothyroxine (Levoxyl, Synthroid) had lower cholesterol levels (Clinical Endocrinology, July 2017). 

Do You Need a Higher Dose?

Your dose of levothyroxine is very low. As a result of your concerns, you might ask your doctor whether it should be adjusted. To prepare to discuss this with your physician, you may wish to read our eGuide to Thyroid Hormones. This 25-page guide describes symptoms of low thyroid function, including elevated cholesterol levels as well as clumsiness and mental fogginess. It also discusses symptoms of excess thyroid hormone, including anxiety, insomnia and heart palpitations. We describe testing and treatment of both conditions.

In addition, you may wish to listen to our interview with thyroid expert Dr. David S. Cooper, Director of the Thyroid Clinic at Johns Hopkins University. We talked to him for Show 1162: How to Treat Common Thyroid Problems

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  1. Patty

    What about new BMJ report re: the over treatment of sub clinical thyroid ?? Is confusing

  2. JIM
    Metro Raleigh, NC

    My primary care physician at the Cooper Clinic in Dallas, TX told me that 20 years ago! Their practice was to adjust intake of Synthroid (T4) until TSH was about 1.0, to reduce cholesterol. For the last few years I’ve added T3 (Cytomel) in the form of compounded sustained release caps, taken twice daily. For me, that combo has been far superior to just T4.

    (BTW, my entire family is hypo-thyroid )

  3. Pattic
    North Texas

    Yes, your hypothyroidism is connected higher cholesterol. Before I was diagnosed 20 years ago with only a tsh of 6 something, my cholesterol was 270 and nothing I did could get it down. I was put on a statin at the same time as thyroid meds but after a year my doctor said, lets see what it does without the statin. It stays around 210 to 220 now. You can look on pubmed.com and see the studies. Another thing, my tsh was 3 until I ate lots of soy protein trying to lower the cholesterol then it went to over 6. That’s when I got diagnosed.

    I’m wondering why they are suggesting lately that us older people don’t need thyroid medicine. I am 75 now. I guess we just need statins. Just being sarcastic…….

  4. Cynthia
    Rehoboth Beach, DE

    This has been a known fact in the veterinary world for a very long time – ie decades. What took doctors so long to figure this out? As a treated ( natural desiccated thyroid ) hypothyroid patient I have personally experienced the reduction in cholesterol and LDL from mild abnormal to normal.

  5. Ann

    I opened this hoping there might be info about low cholesterol. I had a total thyroidectomy in 2014 for multiple nodules (9) that dumped and spiked my thyroid levels at random and also a questionable biopsy. Could not take Synthroid even with T3. But I am doing well on NP thyroid (125) . I battle keeping my cholesterol numbers high enough—- Ive been as low as 118 total. There is so little info available about raising cholesterol on purpose. Even with butter, whole eggs, avocados, and olive oil ample in my daily diet, I rarely get above 156 total cholesterol. my ratios are all good proportionally, just low values. Is it true that a cholesterol below 150 can negatively impact brain and nerve tissues?

  6. Suzy

    I have hypothyroid and hashi’s, but my cholesterol levels are amazing….docs are so happy to see those lab numbers. However, I take NDT – not Synthroid or generic — and I eat an autoimmune paleo protocol diet (no wheat and very few grains, no cow dairy, no sugar) which is very healthy and quite restrictive. It works for me.

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