Basing the investigators study on the evidence that basal serum androgens decrease with age, the investigators hypothesize that women with serum androgens below a certain level could be the population obtaining a benefit of Luteinizing Hormone (LH) supplementation. The objective of the present study is to explore the relationship between basal serum androgen levels and the need of LH for Controlled Ovarian Stimulation (COS) in IVF.

Design: Single centre, open label, randomized controlled trial.

• Population: Patients with indication of In Vitro Fertilization (IVF) with the following criteria:
• Protocol: All patients are tested on day 3-5 of cycle for total Testosterone (Te), Dehydroepiandrosetnodione sulphate (DHEAS) and Androstenodione (Δ4). Samples are frozen and stored at -20ºC for later analysis. FSH, LH, E2, PRL and TSH are also determined. All patients follow Controlled Ovarian Stimulation for IVF with a GnRH agonist long protocol. They are randomized to receive recombinant (r) FSH alone (225 IU/day) or r-FSH + r-LH (225+75 IU/day).
• Sample size calculation: To detect a difference from 40 to 60% (Relative risk: 1.50) on pregnancy rate (PR) between patients with low and high androgen levels with respect to the mean of each COS protocol, with a confidence level of 95% (error α=0.05) and 80% of power (error β=0.2), 97 patients per arm were needed. (n=388 patients). Rounding up, 400 patients are to be recruited.

Inclusion Criteria:

• 1st-2nd IVF cycle
• Regular cycle (25-35 days)
• Age 18 - 42
• BMI: 18-29.9

Exclusion Criteria:

• LH:FSH > 2
• Low response background (< 5 oocytes)
• Recurrent pregnancy loss
• Preimplantational genetic diagnosis indication
• Any systemic, metabolic or endocrinological disorder.