Inclusion Criteria:  Patient with HH and secondary amenorrhea. HH is defined as absence of spontaneous menstruation for ≥6 months, no abrupt menstrual bleeding after progesterone therapy, and normal or low serum FSH and LH levels. The patient gave written informed consent to the study after receiving detailed information and education from medical contributors at the Department of Obstetrics and Gynecology, Medical University of Vienna. Age between >18 and <35 years.  Exclusion Criteria:  Latent or manifest hypothyroidism (TSH >4 micromole/milliliter) or current thyroid hormone replacement therapy. No existing informed consent