Trial design and participants
infertility
OLIGOSPERMIA
The Copenhagen Bone-Gonadal Study is a single-center, double-blinded, randomized clinical trial conducted at the Department of Growth and Reproduction, Copenhagen University Hospital - Rigshospitalet, Copenhagen, Denmark. In brief, infertile men with impaired semen quality and an average duration of infertility of more than 2 years were referred to our andrological center for workup before intracytoplasmic sperm injection (ICSI). Most men had moderate to severe oligospermia, while men with normal sperm count had either very few motile or morphological normal sperm that could explain the long duration of infertility. Inclusion criteria were serum vitamin D level ≤ 50 nmol/L (vitamin D insufficiency) and no serious co-morbidities. Participating men were randomized 1:1 to active or placebo treatment for 150 days. Men in the active group (