What is the most likely mechanism by which testosterone functions inside a cell?

Testosterone achieves his effect by binding to his androgen receptor (nuclear). Because testosterone is steroid hormone (derived from cholesterol), it has a possibility to free diffuse through the cell membrane. When testosterone binds, the receptor undergoes a structural change which allows it to move into the cell nucleus and dimerize. Receptor dimer than binds directly to the specific sequence of the DNA called hormone response element (HRE) which results in regulation of gene expression.

Testosterone functions inside a cell by binding with a receptor protein that enters the nucleus and activates specific genes. Testosterone is the principle male sex hormones in mammals, birds and other vertebrates. Its effects are exerted by; Testosterone can activate the androgen receptor itself or after conversion to 5 alpha dihydrotestosterone by the enzyme 5 alpha reductase.