Hormonal Imprinting: The First Cellular-level Evidence of Epigenetic Inheritance and its Present State

Hormonal imprinting takes place perinatally at the first encounter between the developing hormone receptor and its target hormone. This process is needed for the normal function of the receptor-hormone pair and its effect is life-long. However, in this critical period, when the developmental window is open, related molecules (members of the same hormone family, synthetic hormones and hormone-like molecules, endocrine disruptors) also can be bound by the receptor, causing life-long faulty imprinting. In this case, the receptors’ binding capacity changes and alterations are caused at adult age in the sexual and behavioral sphere, in the brain and bones, inclination to diseases and manifestation of diseases, etc. Hereby, faulty hormonal imprinting is the basis of metabolic and immunological imprinting as well as the developmental origin of health and disease (DOHaD). Although the perinatal period is the most critical for faulty imprinting, there are other critical periods as weaning and adolescence, when the original imprinting can be modified or new imprintings develop. Hormonal imprinting is an epigenetic process, without changing the base sequence of DNA, it is inherited in the cell line of the imprinted cells and also transgenerationally (up to 1000 generations in unicellulars and up to the 3(rd) generation in mammals are justified). Considering the enormously growing number and amount of faulty imprinters (endocrine disruptors) and the hereditary character of faulty imprinting, this latter is threatening the whole human endocrine system.