Teaching Thursday: Liability Threshold

Our Teaching Thursday video-of-the-week is about liability threshold.

This is part of a model of human disease that says that it usually takes multiple “hits” before a cell, a tissue, or even a person suffers disease.

These “hits” can be genetic (say, a mutation); environmental (some sort of chemical insult); or may result from a complex interaction of genetics and environment.

People are born with different genetic, innate differences in disease susceptibility. As they age, they accumulate more and more “hits” which brings them closer and closer to something called the “disease threshold”. The idea is that once you cross the threshold, disease results.

In this video, the disease threshold is a vertical bar toward the right side of the population distributions. The further to the right you are on the curve when you begin life, the higher the chance you’ll have the disease.

The video (I hope) will explain the rest.



2 Comments so far. Leave a comment below.
  1. Rosie,

    I would think that genetics play an even bigger role than you implied. If you are genetically predisposed to a certain disease, then exposure to a precipitating factor would push you over the threshold into disease. However, without the genetic predisposition, exposure might cause other problems, but not the disease in question. For example, without a genetic predisposition to lung cancer, smoking would never result in lung cancer, although emphysema would be a likely outcome. The severity of emphysema would also be the result of genetic factors which determine the degree of damage.

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