Pilot Study on the Effects of FSH Treatment on the Epigenetic Characteristics of Spermatozoa in Infertile Patients With Severe Oligozoospermia

* Inclusion criteria for the infertility treatment group (n=30) 1. Between 25-45 years of age. 2. Total sperm concentration (concentration in millions/mL x volume in mL) between 1-10 million (oligozoospermia) in at least 2 spermiograms obtained after a 2-4 day period of sexual abstinence and with a 7-day separation period between tests. 3. Caucasian. 4. Inability of the couple to become pregnant after one year of sexual relations without using any type of contraception. 5. FSH 2-12 IU/mL. 6. Total testosterone \>300 ng/mL and bioavailable testosterone (calculated with the Sexual Hormone Binding Globulin or SHBG albumin) \>145 ng/dL. * Inclusion criteria for the control group of fertile males (n=15) 1. Between 25-45 years of age. 2. Caucasian. 3. Sperm concentration and motility above the 5th percentile according to the parameters set forth in the 5th edition of the World Health Organization (WHO) guidelines in at least two spermiograms obtained after a 2-4 day period of sexual abstinence and with a 7-day period between tests. 4. Seminal volume \>1 mL. 5. Estradiol \<50 pg/mL 6. FSH \<4.5 IU/L. 7. Total testosterone \>300 ng/dL and bioavailable testosterone \>145 ng/dL. 8. No vasectomy. 9. Has sired a child within the past 5 years. * Exclusion criteria for the infertility treatment group. 1. Total sperm concentration \<1 million. 2. Sperm motility of 0%. 3. History of cryptorchidism, malignant or benign tumors, known chromosomal abnormalities, testicular tor- sion, testicular trauma, orchitis. 4. Drug use in the past 120 days. thyroid dysfunction 5. Medical history:thyroid dysfunction, blood disease, diabetes. 6. Use of anabolic steroids in the past 2 years or for more than 2 years. 7. Body mass index \>30 kg/m . 8. Intake of over 21 units of alcohol/week in the past 120 days.