The Effects of Submaximal Endurance Training/Detraining and Gonadotropin Releasing Hormone Agonists on Growth and Thyroid Hormones Serum Concentrations in Girls with Precocious Puberty

The aim of this study was to investigate the effect of 12weeks endurance training, 4weeks detraining and Gonadotropin releasing hormone agonist (GnRH) on serum levels of growth hormone (GH), triiodothyronine(T3) and thyroxine(T4) in girls with precocious puberty. Twenty-five girls age 6-8 (average height of 124cm and weight of 27.3 kg) with precocious puberty were randomly divided into three groups (medication, training, medication+training) and 10 healthy girls (No precocious puberty) with the same average height and weight were also included as control group. Serum levels of GH, T3, and T4 were measured at baseline by ELISA technique. Then the experimental groups were subjected an endurance training program three days/week with 20-75 min per day with 45-75% of maximum heart rate for 12 weeks. The medication groups also received GnRH agonist during the study, once monthly (1ml/four weeks) by intramuscular injection. GH, T3, and T4 serum levels were measured again 48 hours after the last training session and also after four weeks of detraining. The repeated measures ANOVA showed that 12weeks of endurance training alone, as well as 12weeks of endurance training+GnRH agonists, reduced GH,T3 and T4 levels and after detraining, GH and thyroid hormones concentrations approximately return to pre-workout levels. Medication reduced GH level after 16 weeks but could not effect on thyroid hormones. According to these findings, aerobic training and the use of the GnRH agonists can have a positive effect on hormonal function in girls with precocious Puberty but detraining eliminate the benefits of training in girls with precocious puberty.