Monitoring testosterone replacement therapy - a strategy for distinguishing real and falsely high concentrations of testosterone.

During the monitoring of the hormone status of transmen, higher testosterone
levels than expected are regularly found.
One possible explanation is that it is caused by phlebotomy from the elbow on
which on the testosterone gel is applicated. In the body, testosterone is
converted to estradiol, which results in a correlated rise in estradiol in case
of a high testosteron. Hoewever, this is not the case for testosterone from the
phlebotomy site, which theoretically results in a higher testosterone/estradiol
ratio.
Another possible explanation for higher than expected testosterone
concentrations is that the gel was applied on the forearm, distal to the
venipuncture site, causing a high testosterone concentration in the venous
bloodstream of that arm.

If this is the case, this is of great importance for patients and health care
providers in clinical practice.

By analysing existing data, testosterone gel users turned out to have a higher
testosterone/estradiol ratio than testosteron injection users.
This assumes we're on the right track.

The goal of this study is to asses wheter testosterone contamination is caused
by appliction of testosterone gel on the phlebotomy site or on the forearm.
If previously mentioned study is supported by the current study, the
testosterone/estradiol value can be used in clinical practice to detect falsely
high testosterone levels and hence upgrade the quality of care.

We would like to take blood of 7 transmen, from the gel applied arm and from
the other arm

One extra venapunction at a moment when blood is already taken