You don't typically cycle hGH.
That's done for anabolic-androgenic-steroids, which can have some serious side effects that become more pronounced over time. Particularly if you are younger.
hGH is usually a permanent decision, though the amount you utilize can change higher/lower depending on your goals and its effectiveness.
No shrinkage of pecker on anything -- your testes can shrink on AAS as they dont need to produce test as they detect highg levels from your AAS input. Don't expect any big strength gains or size gains. Do expect many other beneficial effects. Including fat loss, healing, recovery, and noticeable improvement to skin, collagen and hair. It can get pricey depending on your source and the amount taken.
If you have insurance (or can afford it) I would always encourage getting a full blood-panel from the doctor to see what your current levels are for GH and everything else before you begin. Especially at your age.
This can be a very healthy (and happy) lifestyle change. Good luck.