Desmosterol Test

Desmosterol is a molecule your body uses to make cholesterol. It’s one of the final steps in the Bloch pathway, one of the two main routes your body uses to produce cholesterol internally. By measuring desmosterol in your blood, we can get a better sense of how much cholesterol your body is making, separate from the cholesterol you get from food.

Standard cholesterol tests like LDL-C reflect how much cholesterol is circulating in your bloodstream, but they don’t tell us where it’s coming from. Desmosterol gives us a window into your body’s cholesterol production rate, which helps determine whether elevated cholesterol is driven by diet or by overproduction within the body.

• High desmosterol suggests your body is making too much cholesterol, which can push up LDL and ApoB levels and raise the risk of heart disease. These individuals are often the best responders to cholesterol-lowering medications like statins.
• Low desmosterol is commonly seen in people taking statins, since these drugs reduce cholesterol production.
• Very low desmosterol in those not taking statins could indicate an impairment in cholesterol production, which may have downstream effects on cell membranes, hormone production, or nerve repair.

In clinical practice, desmosterol is often measured alongside lathosterol to give a more complete picture of how your whole body is making cholesterol. Since different tissues use different pathways (Kandutsch-Russell vs Bloch), measuring both markers can help clinicians better understand which treatments may be most effective.

Desmosterol and Brain Health: A Developing Area

Cholesterol is essential for brain function. Your brain relies on it to grow, form and repair connections, and keep nerves insulated and working properly. One of the main ways the brain makes cholesterol is through a pathway that uses desmosterol (known as the Bloch pathway). Because of this, researchers are studying desmosterol as a possible indicator of how the brain is producing cholesterol.

While plasma desmosterol (from a blood test) doesn’t directly measure levels inside the brain, studies show it closely reflects brain levels—making it a useful and non-invasive marker. (The only way to directly measure brain desmosterol is through a spinal tap, which is rarely done outside of research.)

Some studies have found that people with mild cognitive impairment or Alzheimer’s disease tend to have lower levels of desmosterol in their blood. In these individuals, lower desmosterol has also been linked to greater declines in memory and thinking skills.

Still, the connection isn’t fully understood. Does low desmosterol contribute to cognitive decline, or is it just a side effect of changes already happening in the brain? We don’t yet know.

One complicating factor is that certain cholesterol-lowering medications can cross into the brain and potentially suppress desmosterol production there. No studies controlled for these medications, which makes it harder to draw conclusions.

For now, some physicians may choose to keep a closer eye on desmosterol in people with a family history of dementia or who carry the APOE E4 gene, particularly if they’re also on a statin. But this remains a developing area, and more research is needed to understand whether changes in desmosterol are a cause, an effect, or simply a marker of brain health.