My personal experience as a female, with a lifetime of low blood pressure.
I have not done much high altitude trekking. Two times in recent memory, as an adult, and both times I noticed significant peripheral edema in hands and feet as I descended. I ascended 3000 feet the first time (that's feet, not metres, so not very high at all), and 2500 feet the second time, on day hikes.
In addition to the edema, on the second time (and maybe on the first time but I didn't understand what was happening so I may not have connected the symptoms to the hike) I had insomnia afterwards, difficulty eating/digesting food, lack of appetite, developed a cough, did not feel good at all, breathing patterns were not normal and my pulse was not regular. Symptoms continued into the next day.
I did not get a headache the second time. I don't remember the first time.
I live at sea level.
I am not surprised that my body reacts this way, having lived with low blood pressure all my life. It seems I have to keep moving to keep my blood flowing. It's the vessel walls that are too dilated and slack that cause this in my opinion and experience. There is some family history too.
I get migraines caused by vasodilation from hormone fluctuations and it is cured quickly and easily with sumatriptan, a drug which causes vasoconstriction. I noticed sumatriptan is one drug of choice in treating altitude sickness.