Prealbumin Test

Prealbumin, now more commonly called transthyretin, is a protein found in your blood that plays important roles in transporting vital substances. Its main jobs are carrying thyroid hormone (specifically thyroxine, or T4) and partnering with another protein, retinol-binding protein, to transport vitamin A. Despite its old name, “prealbumin” is not related to albumin production but was named because it moves faster than albumin on certain laboratory tests.

Biologically, prealbumin is built from four identical parts, called subunits, each made up of 127 amino acids. Together, they form a stable structure known as a tetramer. This strong, compact design not only helps prealbumin carry thyroid hormone and vitamin A efficiently but also prevents the protein from falling apart too easily under normal conditions. However, if the tetramer breaks apart—a process called dissociation—it can misfold and clump together, leading to diseases called amyloidoses, which can harm nerves or the heart.

The gene responsible for making prealbumin is located on chromosome 18. In addition to being made in the liver and released into the blood, it is also produced in the eye and brain, helping maintain healthy tissues in these areas.

Clinically, prealbumin is extremely valuable as a nutritional biomarker. Because it has a short half-life (about 2 days), its blood levels change quickly in response to shifts in nutrition or illness. Low prealbumin levels often signal malnutrition, inflammation, or serious disease. For example, people in the hospital with very low prealbumin levels are at a higher risk of dying, even after accounting for other risk factors. Prealbumin also rises quickly with effective nutritional support, making it useful for monitoring recovery. Additionally, in older adults with type 2 diabetes, low prealbumin levels have been linked to a higher risk of osteoporosis, suggesting it plays a broader role in overall health.

That said, low levels do not always mean someone is simply undernourished—they may also reflect an active disease process. Prealbumin levels can drop due to inflammation, infection, liver disease, and certain chronic illnesses.