Measurement of steroid hormones by mass spectrometry does provide distinct advantages. First due to the flexibility of the instrument multiple analytes can be measured in a single run which allows for reporting of several analytes in one sample  . Additionally, the use of mass spectrometry can support the large dynamic range typically seen in steroid hormones , where concentration ranges within analytes can vary significantly (., testosterone concentrations < 10 ng/dL can be observed in women and children and concentrations over 1000 ng/dL can be seen in men)  . Additionally, it can support differences in the concentration range between analytes; for example, testosterone in men as high as 1000 ng/dL can be measured in the same sample with an estradiol concentration as low as 10 pg/mL  .
Testosterone can be administered parenterally , but it has more irregular prolonged absorption time and greater activity in muscle in enanthate , undecanoate , or cypionate ester form. These derivatives are hydrolyzed to release free testosterone at the site of injection; absorption rate (and thus injection schedule) varies among different esters, but medical injections are normally done anywhere between semi-weekly to once every 12 weeks. A more frequent schedule may be desirable in order to maintain a more constant level of hormone in the system.  Injectable steroids are typically administered into the muscle, not into the vein, to avoid sudden changes in the amount of the drug in the bloodstream. In addition, because estered testosterone is dissolved in oil, intravenous injection has the potential to cause a dangerous embolism (clot) in the bloodstream.
Sex hormone-binding globulin (SHBG) is thought to mainly function as a transporter and reservoir for the estradiol and testosterone sex hormones. However it has also been demonstrated that SHBG can bind to a cell surface receptor (SHBG-R). The SHBG-R has not been completely characterized. A subset of steroids are able to bind to the SHBG/SHBG-R complex resulting in an activation of adenylyl cyclase and synthesis of the cAMP second messenger.  Hence the SHBG/SHBG-R complex appears to act as a transmembrane steroid receptor that is capable of transmitting signals to the interior of cells.