FSH level correlates inversely with the number of eggs in the ovaries - it is a marker of ovarian reserve. A low ovarian reserve may indicate fewer available eggs and can lead to infertility. In this case synthetic FSH by injection or Clomid (Clomiphene citrate) via a pill can be given to stimulate follicles to mature in the ovaries.
FSH in males is important for both, formation and maturation of the sperms. The low levels of FSH leads to low sperm count (oligospermia). It can one of the reasons for infertility. However, chances are good if the female partner is fertile; many couples with this problem have been successful.
In more severe cases IVF (in vitro fertilisation), or IVF – ICSI (intracytoplasmic sperm injection) is done and is often the best option, specifically if time is a factor or fertility problems coexist on the female side.