PSA levels will increase over time, depending on the level of testosterone - Part I

[janebob99]

Here's a schematic plot of the increase in PSA level (or increase in tumor volume) over time, for various levels of testosterone (while the tumor is relatively small).

At very low levels of testosterone (for example, T = 10 ng/dL), the increase in PSA level is very small after a given time (for example, time = 1 year) because the tumor is growing very slowly.

However, at higher levels of testosterone (50-300 ng/dL), the PSA levels after time = 1 year are much greater (because the tumor is growing a much faster rate).

Finally, at higher levels of testosterone (T = 300 - 1400 ng/dL), the PSA level at time = 1 year reaches a maximum value, due to the saturation effect. In other words, for T > 300 ng/dL, the tumor growth rate (slope of the line) has reached a maximum value (speed).

Think of it as a speed limiter on your car...above a certain speed limit, you can't make the car go faster, despite pushing harder on the gas pedal. That's what happens when T > 300 ng/dL, namely, the PSA growth rate becomes fixed at a constant value and doesn't increase any more as you increase testosterone beyond about 300 ng/dL.

A moving automobile is a good analogy. The PSA value (or tumor size) is equivalent to the distance travelled over a given amount of time. The car's speed (velocity) is equivalent to the Tumor Growth Rate or PSA growth rate. Finally, the testosterone level is equivalent to the gas pedal's position. Increasing the level of testosterone is equivalent to pushing harder on the gas pedal...it makes the car go faster.

For example, doubling the testosterone level from 100 to 200 ng/dL makes the PSA increase at double the rate.

On the other hand, increasing the testosterone level to greater than T = 300 ng/dL will not make the PSA growth rate increase any more (because of the saturation effect that Morgentaler discovered). It becomes fixed at a constant growth rate (speed) because the Androgen Receptors have become saturated with testosterone (DHT) molecules.

Hope this is helpful.

Bob