Even if it is not hereditary, it is worth mentioning the McCune-Albright syndrome that can also predispose patients to pituitary tumors. This is a very rare disease with a prevalence ranging between 1:100.000 and 1:1.000.000. Although not inherited, it is genetically determined, as somatic mutations have been identified in the majority of patients. Mutations responsible for McCune-Albright syndrome are found in the gene encoding the alpha subunit of G-proteins (Gsα) termed GNAS gene (GNAS Complex Locus, previous name: GNAS1 - Guanine Nucleotide Biding Protein, Alpha-Stimulating Activity Polypeptide 1) and are activating the protein function (gain-of-function mutáció). The mutation is found in several organs and cells of the affected patients, but not in all. This phenomenon is termed genetic mosaicism, where multiple cell lines with different genetic composition are present in the individual. It is hypothesized that the mutation responsible for the McCune-Albright syndrome arises in the early postzygotic stage that can explain why organs from different germ layers are affected. The mutation would be incompatible with life if it were germ-line. The most characteristic features of McCune-Albright syndrome include café-au-lait spots of the skin, polyostotic fibrous dysplasia and precocious puberty. Hypogonadotropic (gonadotropin independent) precocious puberty is the most common endocrine disease in McCune-Albright syndrome. Girls are more often affected. In both sexes, precocious puberty is characterized by the early appearance of secondary sexual features (pubic hair, pubarche), early vaginal bleeding and breast growth (early thelarche) in girls, testicle and penile growth in boys. Among pituitary tumors, acromegaly is most often observed in McCune-Albright syndrome, but prolactinoma can also occur. Apart from these thyroid nodules, hyperthyroidism and cortisol-secreting adrenocortical adenoma resulting in Cushing syndrome can also occur.