They're not complications, per se, I would stress that many men find ancillary problems on their HRT journey. Thyroid, being one, brain chemistry and neurotransmitters another, Pituitary, adrenals, you can go on and on. HRT is far more complex than Testosterone. One thing I say to my nurse practitioner who while curious, actually doesn't really approve, which isn't up to her, but I've said straight faced..."I'll take Test before I take the chemicals and poisons that come from your Rx pad".
You'll have to figure out WHY you want to go down this road. Symptoms really bothering you? Or are you looking at a number on a test that says your Low T? What do you want out of this, what are you trying to "fix"? Ask yourself these questions.