How it works
Testosterone binds the androgen receptor across tissues and is locally converted to dihydrotestosterone (5α-reductase) and estradiol (aromatase). Replacement restores normal androgen and downstream estrogen signaling.
The evidence
The Testosterone Trials (TTrials) in men over 65 with low T showed improvements in sexual function, mood, walking distance, and anemia. Current Endocrine Society guidelines support TRT in men with consistently low morning total T (<300 ng/dL) and clinical symptoms.
Typical dosing
Common regimens: testosterone cypionate 100–200 mg weekly intramuscular or subcutaneous, often divided into two weekly doses. HCG 250–500 IU twice weekly may be added to preserve testicular function and fertility.
Side effects
Common
- Acne
- Increased red blood cell count (hematocrit rise)
- Mild fluid retention
Less common
- Elevated estradiol
- Sleep apnea worsening
Rare
- Polycythemia requiring phlebotomy
- Suppressed spermatogenesis (mitigated with HCG)
Drug interactions
- Anticoagulants — increased bleeding risk with rising hematocrit
- Aromatase inhibitors (anastrozole) — added when estradiol elevates
- Insulin — may need dose adjustment as body composition changes