Stres ve Demansta Hipotalamus-Hipofiz-Adrenal Ekseninin Rolü

Öz

AbstractThe Role of the Hypothalamic-Pituitary-Adrenal Axis on Stres and Demantia An organism responds to a stressor with activation of the hypothalamo-pituitary-adrenal axis, culminating in the secretion of glucocorticoids from the adrenal cortex. Activity of the hypothalamo-pituitary-adrenal axis is regulated by a negative feedback loop that dampens central drive of the axis via the actions of the secreted glucocorticoids. Conversely, under conditions of chronic stress, glucocorticoids delivered centrally increase hypothalamic paraventricular nucleus corticotrophin releasing factor expression and cortisol level increases based on this. Gonad hormones in the stress induced hypothalamo-pituitary-adrenal axis activity, inhibits the rising of cortisol levels by increasing the sensitivity against glucocorticoids. However, clinically healthy elderly subjects and demented patients, particularly those with Alzheimer disease, had significantly higher cortisol levels.

Anahtar Kelimeler

• hypothalamo-pituitary-adrenal axis, stress, demantia

Stres ve Demansta Hipotalamus-Hipofiz-Adrenal Ekseninin Rolü

Öz

Bir canlı, stres etmeni ile karşılaştığı zaman bir seri eşgüdümlü yanıtlar verir. Adrenal korteksten yüksek seviyede glukokortikoid salgılanmasına yol açan hipotalamus-hipofiz-adrenal ekseninin aktivite kazanması da bunların içindedir. Hipotalamus-hipofiz-adrenal ekseninin aktivitesi bir negatif geribildirim döngü ile düzenlenir. Bunu sağlayan, bu eksenin merkezi güdümünü denetleyen glukokortikoidlerdir. Kronik stres koşullarında tersine, glukokortikoidler hipotalamustaki paraventriküler nükleusdan kortikotropin salgılatıcı faktör ekspresyonundaki artışı baskılayamazlar ve kortizol buna bağlı olarak yükselir. Stresle değişen hipotalamus-hipofiz-adrenal eksen aktivitesinde, gonad hormonları glukokortikoidlere karşı duyarlığı artırarak kortizol yükselmesini önlemektedirler. Ancak kortizol seviyesi; yaşlı bireylerde, demanstaki hastalarda ve alzheimer hastalarında, oldukça yüksektir. Yüksek kortizol, öğrenme ve uzun süreli belleği engellemektedir.

Anahtar Kelimeler

• hipotalamus-hipofiz-adrenal ekseni, stres, demans

Kaynakça

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