Every Patient with Any Lipid Disorder is Hypothyroid - Until Proven Otherwise

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These are the lipid levels of a 53-year-old woman admitted with an acute coronary event.

Her initial LDL levels look like an inherited LDL receptor defect, either heterozygous or even homozygous because the values are so high.  But her TSH was 231 IU/L, her T4 was <1 pg/nl and her T3 was <0.5 pg/nl, all classic for severe hypothyroidism.  The third set of lipid numbers are hers on atorvastatin 80, ezetimibe 10, and levothyroxine 112 mcg.

Hypothyroidism is a frequent cause of lipid disorders.  I remember my first experience.  I was trying to fix a surgeon’s lipids, but he was too busy to see me in the office.  He had a poor response to statins, so I finally insisted we move our visits from the corridor to my office.  My nurse ordered the pre-visit lipids I require of all patients, which included a TSH.  It was markedly elevated.

Hypothyroidism can cause the full spectrum of lipid disorders. (*)  Thyroid hormone is required for normal low density lipoprotein (LDL) receptor function.  Indeed, T3 activates the gene that upregulates the LDL receptor, so low thyroid levels can mimic a genetic LDL receptor defect.  Since most of the drugs that lower LDL do so by upregulating LDL receptor activity, hypothyroidism reduces the lipid-lowering effect of drugs including statins.  Thyroid hormone is also needed for normal function of lipoprotein lipase, the enzyme that facilitates triglyceride clearance, and which also increases HDL cholesterol.  Thyroid hormone facilitates the action of lecithin cholesterol acyl transferase (LCAT), which has a vital role in filling the high-density lipoprotein (HDL) particle with cholesterol.   So a low HDL-C and high TGs are also possible, but infrequent, manifestations of hypothyroidism, . 

So, the rule is:  every patient with a lipid disorder is hypothyroid until proven otherwise.

*Rizos CV, Elisaf MS, Liberopoulos EN. Effects of Thyroid Dysfunction on Lipid Profile. Open Cardiovasc Med J. 2011; 5: 76–84. PMID: 21660244