Got this exerpt from an article by Dr David Speer:
Growth hormone, however, causes A.D.H. (Anti-Diuretic Hormone) to go up. ADH is a very potent coronary constrictor which also constricts veins. It is produced starting in the hypothalamus. The nerve endings of certain neurons in the hypothalamus reach into the posterior pituitary, and ADH and oxicitocin come from the posterior pituitary. ADH can go up to 20 times normal levels with fear, or anger, and stress. This can cause coronary constriction within minutes, and this can cause a massive heart attack.
Growth hormone makes ADH go up, and as a direct effect of this, water retention goes up, which causes higher blood pressure. ADH is dose dependent of GH, which is why you have to drop the dose if blood pressure goes up too high, until your circulatory system adjusts to handle it. This is the only bad side effect of an otherwise very good dose of growth hormone.
Prohormone precursors (eg., androstenedione) can aromatize directly to estrogen. So don't take androstenedione, or androstenediol, etc. They are all more likely to aromatize to estrogen than testosterone. Arimidex protects you from aromatization from all of them. Arimidex is a breakthrough, it is breakthrough medicine. Everybody (men and women) should probably be on 1 pill of Arimidex per week.
If somebody is taking GH and also testosterone, then they are getting increased water retention from the increase in ADH, and also increased sodium retention from elevated testosterone. Aromatization of testosterone increases with age. So if you take Arimidex, you block the conversion of testosterone to estrogen. This then helps to reduce water retention due to elevated estrogen. If you also take clonidine, this stops elevated ADH, which stops the active water retention.