Hi Sarah,
HRT will soften your features in general. Where it does so is subtle, and hard to define. I've been on low dose for 22 months now and look younger than my given age, and I'm in the 35-40 bracket.
In answer to your question, the area around your brow is more due to folding of the skin from the underlying muscle tensing.
The area under your eyes almost seems like venous pooling. This can often occur as a result of chronic upper airway obstruction. If you happen to have high blood pressure and your BMI is on the high side, a bit of weight loss may resolve the issue, but if you have any concerns on that front, a visit to the ENT to screen for sleep apnea may not be remiss.