You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Resumption of menstruation and pituitary response to gonadotropin-releasing hormone in functional hypothalamic amenorrhea undertaking estrogen replacement therapy. Background: Functional hypothalamic amenorrhea (FHA) refers to a functional menstrual disorder with various causes and presentations. Recovery of menstrual cyclicity is common in long-term follow-up but the affecting factors remain unknown. Aim: To explore factors affecting the menstrual resumption and to evaluate the pituitary response to gonadotropin-releasing hormone (GnRH) in FHA. Materials and Methods: Thirty cases with FHA were recruited. All subjects were put on continuous 1mg/day estradiol valerate orally and followed up monthly. Recovery was defined as the occurrence of at least three consecutive regular cycles. Responder referred to those who recovered within two years of therapy. Gonadotropin response to the 50 microgram GnRH challenge was tested every three months. Results: Nineteen (63.3%) subjects recovered with a mean time to recovery of 26.8 months. Time to recovery was negatively correlated with body mass index (BMI) before and by amenorrhea. Twenty-one cases had undertaken therapy for more than two years and ten of them recovered. BMI before and by amenorrhea were negatively correlated with the recovery. Significant increase of serum luteinizing hormone (LH) and LH response to GnRH were noted after recovery. Conclusions: Menstrual resumption was common in FHA undertaking ERT. The likelihood of recovery was affected by their BMI before and by amenorrhea but not by the weight gain during therapy. Low serum LH and attenuated LH response to GnRH were the main features of pituitary deficiency in FHA. The menstrual resumption in FHA was accompanied by the recovery of serum LH and the LH response to GnRH.
{"Chemical": ["gonadotropin-releasing hormone", "estrogen", "estradiol valerate", "GnRH"]}