<s>[INST] Hello doctor, I am a female. I was diagnosed seven years ago for central precocious puberty and was treated with three annual implants of Histrelin. The third implant still has not been removed after about four years. I have looked at procedure guidelines online that say that the implant must be removed after a year is up. Does it have to be removed? What will happen if it is not removed? Also, I am showing no signs of puberty except pubic hair and height. Is it possible that the Histrelin is holding my growth? [/INST] Hi. Yes, Histrelin implant should have been removed after one year. Please speak about this to your doctor. Histrelin implant is a synthetic analogue of gonadotropin-releasing hormone (GnRH) agonist. It works by decreasing the production of certain hormones, which reduces estrogen and testosterone levels in the body initially. Laboratory tests, including luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol, testosterone levels, or height and bone age may be performed to monitor your progress or to check for side-effects. I would suggest you to carry out all the hormonal profile that is FSH, LH, testosterone levels, thyroid levels, estradiol levels to see that they are in normal range. Periods are related to circulating estrogen levels. </s>