The study is designed to answer the following questions:

1. Is there any difference between the compositions of the HDL cholesterol subpopulations of patients with hypogonadism and the healthy controls.
2. What is the effect of testosterone replacement therapy on the distributions of HDL subgroups.
3. Is there any difference between the effects of the two different testosteron replacement regiments

This study has two designs:

1. The case control design to search for the difference between the HDL subgroups and the other metabolic parameters between the healthy subjects and the patients with hypogonadism
2. The follow-up study to search for the effects of two different testosterone replacement regiments.

Inclusion Criteria:

• Congenital hypogonadotrophic hypogonadism,
• Male sex

Exclusion Criteria:

• Previous history of androgen replacement,
• any chronic disorder