Since 1966, many studies have referred to the incidence of transsexualism. The ratio between MFTs and FMTs has varied, depending on surgeons’ willingness to perform the operation. Because male-to-female surgery is less complicated, there have been more MFTs. In countries with highly specialized surgeons, such as Serbia, the number of transsexuals has been the same (male-to-female and female-to-male) [9]. In Table 6.2, the incidence of transsexualism is shown.

In some studies, the number of patients was too small. In human biology the incidence of many disorders is the same in males and females and it would be difficult to explain such a high difference in ratio, except with some technical details regarding the operations.

A team of three highly educated psychiatrists in the field of sexual disorders confirm the diagnosis after 1 year or more of follow-up. They have to exclude many psychiatric disorders such as transvestitism, homosexuality etc. After that the endocrinologist examines the patient, detects the karyotype and carries out hormonal analysis. It is necessary to take blood samples in MFTs for follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin, estradiol, progesterone, testosterone, SHBG, 17 OH progesterone, free thyroxine, thyroid-stimulating hormone (TSH), and cortisol. In FMTs on day 7 of the menstrual cycle (for those younger than 30 years of age) blood samples are taken for FSH, LH, prolactin, estradiol, testosterone, androstenedione, dehydroepiandrosterone sulfate (DHEAS), 17 OH progesterone (to exclude congenital adrenal hyperplasia), fT4, TSH, cortisol and on day 21 progesterone is measured. According to these results endocrine diseases mimicking transsexualism can be excluded such as androgen-secreting tumors, congenital adrenal hyperplasia, pseudohermaphroditism of other different origins, and some other endocrine diseases, such as thyroid and adrenal gland diseases. A complete internal examination and an ultrasound of the gonads (ovaries or testis) and breasts are obligatory.

After confirming diagnosis from the endocrine point of view therapy regarding the characteristics of the opposite sex can be initiated. Sperm of MFTs can be frozen if desired and FMTs can store their follicles in case they want to have a biological child later on.

The aim of the therapy is to help a patient to look like a person they feel that they can depend upon to provide normal sexual function and work abilities, and to determine the dosage of the therapy individually.