Cholesterol and progesterone play vital roles in the human body. One major role is reproduction. Both may affect fertility, pregnancy, and miscarriage.

Cholesterol and progesterone both have important effects on the body. Though they work through different mechanisms, each is involved in reproduction.

You may have heard of cholesterol in relation to plaque buildup in arteries, but it is also a precursor that helps make estrogen and progesterone.

Your levels of cholesterol and progesterone can affect both fertility and pregnancy.

Cholesterol is made in the liver and has many important roles in the body. It is a key part of cell membranes, helps produce bile acid, and assists in the synthesis of vitamin D. It also helps produce certain hormones, including steroid hormones like estrogen and progesterone.

The liver also produces the lipoproteins HDL and LDL, which are responsible for transporting cholesterol in the blood. The term “LDL cholesterol” refers to the cholesterol that LDLs carry. “HDL cholesterol” is cholesterol carried by HDLs.

The body typically has higher levels of LDL cholesterol than HDL cholesterol. LDL cholesterol, along with other types of non-HDL cholesterol, is the type of cholesterol doctors typically refer to as “high cholesterol.”

LDL cholesterol is often known as “bad cholesterol” and is the type that is often helpful to reduce. It’s rare to have too much HDL cholesterol, but it can happen.

Progesterone is an important hormone with many functions in the body, particularly those related to the reproductive system.

Progesterone is a type of hormone called a steroid hormone. All steroid hormones are derived from cholesterol.

The body uses cholesterol as a building block to create progesterone. This process involves enzymes. First, cholesterol is converted into pregnenolone using the enzyme P450scc. Then the enzyme 3β-HSD turns this into progesterone.

Progesterone can be produced in different parts of the body, such as the:

It’s also thought to be produced in the brain.

In the middle of the menstrual cycle, the corpus luteum produces progesterone to help prepare the body for the implantation of a fertilized egg.

Progesterone keeps the uterus lining thick and stimulates the development of new blood vessels, ready for egg implantation. This means when the egg is fertilized, it can implant and will have a supply of blood vessels that nutrients can travel through.

In males, the adrenal glands produce progesterone to aid sperm development.

Imbalances in cholesterol can have a knock-on effect on progesterone, as cholesterol is required for the synthesis of this hormone.

During pregnancy, cholesterol levels increase to support fetal growth and development and enable the pregnant person to produce healthy breast milk.

Maternal blood cholesterol may increase by 30% to 40%. Since cholesterol is used to produce progesterone, this rise is to allow more progesterone to be produced.

If cholesterol levels get too high, however, hypercholesterolemia may occur. In pregnant people, this is known as gestational hypercholesterolemia or maternal hypercholesterolemia.

An imbalance of blood lipids (dyslipidemia) can be dangerous for both the pregnant person and the unborn child and may cause cardiovascular effects.

According to a 2019 study, the regulation of cholesterol and progesterone metabolism may have a role in miscarriage.

During pregnancy, cells called extravillous trophoblasts (EVTs) create a blood supply to the fetus. Problems with this cell type have been linked to complications in both the pregnant person and the fetus.

The 2019 study looked at human EVTs from first-trimester placental tissues. Researchers found that the way cholesterol levels are regulated is different in these cells, and the levels of cholesterol are higher.

The study also shows that these EVTs can secrete progesterone. Lower levels of cholesterol were found to decrease the amount of progesterone produced by these cells.

Additionally, an enzyme involved in producing progesterone was found to be lower in EVTs that had been associated with spontaneous abortions. This suggests that the issues with progesterone metabolism may have a role to play in early miscarriages.

Both progesterone and cholesterol have important roles in reproduction.

Monitoring and maintaining proper levels of both cholesterol and progesterone are crucial for ensuring optimal fertility, a healthy pregnancy, and successful outcomes for both parent and baby.