Monday 9 January 2017
- Hormonal hyperplasia is best exemplified by the proliferation of the glandular epithelium of the female breast at puberty and during pregnancy and the physiologic hyperplasia that occurs in the pregnant uterus.
- The experimental model of partial hepatectomy has been especially useful in examining the mechanisms that stimulate proliferation of residual liver cells and regeneration of the liver.
- Similar mechanisms are likely involved in other situations when remaining tissue grows to make up for partial tissue loss (e.g., after unilateral nephrectomy, when the remaining kidney undergoes compensatory hyperplasia).
- Hyperplasia is generally caused by increased local production of growth factors, increased levels of growth factor receptors on the responding cells, or activation of particular intracellular signaling pathways.
- All these changes lead to production of transcription factors that turn on many cellular genes, including genes encoding growth factors, receptors for growth factors, and cell cycle regulators, and the net result is cellular proliferation.2 In hormonal hyperplasia, the hormones may themselves act as growth factors and trigger the transcription of various cellular genes.