What is hyperplasia -

Ans. is 'c' i.e., Increase in cell number Hvperplasia o Hyperplasia is an increase in the number of cells without increase in size in an organ or tissue (by contrast hyperophy refers to an increase in the size of cells). o Hyperplasia takes place if the cellular population is capable of synthesizing DNA, thus permitting mitotic division i.e., hyperplasia involves cell division (by contrast hyperophy involves cell enlargement without cell division). o Hyperplasia can be physiological or pathological. A. Physiological hyperplasia o It occurs when there is increased physiological demand e.g (a) Hormonal --> Hyperplasia of endometrium in pregnant uterus, proliferation of the glandular epithelium of female breast at pubey and during pregnancy. (b) Compensatory --> Increase in tissue mass after damage or paial resection, e.g. regeneration of liver after paial hepatectomy. B. Pathological hyperplasia o It occurs when there is increased stimulus under ceain pathologic conditions. o Most forms of pathological hyperplasia are caused by excessive hormonal stimulation or growth factor acting on target cells, e.g., Endometrial hyperplasia due to disturbed estrogen and progesterone balance (with relative excess of estrogen) in menstural cycle. Note : Stimulus for physiologic and pathologic hyperplasia may be the same (e.g., estrogen for endometrial hyperplasia), but in physiologic hyperplasia, the stimulus is due to normal physiologic changes of body e.g., pregnancy, while in pathologic hyperplasia the stimulus is due to ceain pathologic conditions e.g., estrogen secreting ovarian tumor. o Although pathological hyperplasia is abnormal, the process remains controlled --> Hyperplasia regresses if the hormonal stimulation is eliminated. o It is the response to the normal regulatory control mechanisms that distinguishes benign pathological hyperplasia from Cancer, in which the growth control mechanism becomes defective. o However, pathological hyperplasia constitues a feile soil in which cancerous proliferation may eventually arise --> e.g., patients with endometrial hyperplasia are at increase risk of endometrial carcinoma Mechanism of hyperplasia o Hyperplasia is caused by increased production of growth factor or hormones that lead to production of transcription factor that turn on many cellular genes and induce cellular proliferation. o After some type of cell loss, hyperplasia is caused not only by proliferation of cells but also by the development of new cells from stem cells --> e.g., After hepatectomy the hyperplasia is due to proliferation of the remaining hepatocytes, but in chronic hepatitis, intrahepatic stem cells play a major role in hyperplasia as the proliferative capacity of hepatocytes is compromised.