Under what conditions are HDLs formed and sent out?

HDLs, or high-density lipoproteins, are formed primarily in the liver and play a crucial role in lipid metabolism, particularly in the transport of cholesterol. They are involved in the reverse transport of cholesterol, taking excess cholesterol from peripheral tissues and bringing it back to the liver for excretion or repurposing.

When the liver has low levels of cholesterol, it responds by producing more HDL particles. This formation helps to balance the body's lipid levels, ensuring that excess cholesterol is efficiently cleared from the bloodstream. Low cholesterol levels in the liver will signal a need to increase HDL production to help facilitate the removal of cholesterol from other tissues and prevent plaque formation in blood vessels.

Thus, the condition of having low cholesterol in the liver directly influences the formation and release of HDLs, making this the correct answer.