 A six month study of ACP-001, a long-acting growth hormone product, versus standard human growth hormone therapy. ACP-001 will be given once-a-week, standard human growth hormone hGH will be given on a daily basis. The primary aim is to demonstrate safety, pharmacokinetics and pharmacodynamics over a period of six months. A secondary objective is the comparison of height velocity HV of the ACP-001 treated groups to the daily hGH treatment group. 