Adrenocorticotropic Hormone.ppt

ADRENOCORTICOTROPIC HORMONE

1. 1
Adrenocorticotropic Hormone
(ACTH)
Introduction
•ACTH is the hormone of the anterior
pituitary.This hormone also called
corticotropin.Enhances the production of
adrenal androgens.
Source
•ACTH is mainly secreted by the basophilic
chromophilic cells of the anterior pituitary.

2. 2
•The secretion of ACTH controls by a
releasing factor called corticotropin-
releasing factor. (CRF) It is secreted into
the median eminence of the hypothalamus
and then carried to the anterior pituitary
gland,where it induces ACTH secretion.
Chemistry
•ACTH is a large polypeptide ,having a
chain length of 39 amino acids

3. 3
Plasma level and Half-life
•The daily output of this hormone is 10 ng
and the conc.in plasma is 3 ng/dl.
•Half-life of ACTH is 10 minutes.
Mode of action ACTH:
•ACTH acts by the formation of cyclic AMP.

4. 4
Actions
Adrenal actions:
•Actions of ACTH on Adrenal Cortex
•Maintenance of structural integrity and
vascularization of zona fasciculata and zona
reticularis of adrenal cortex.
•Conversion of cholesterol in to
pregnenolone,which is the precursor of
glucocorticoids.

5. 5
•Adrenocorticotropic hormone is
responsible for synthesis of
glucocorticoids.
•Release of glucocorticoids.
•Prolongation of glucocorticoid action on
various cells.
Non adrenal actions of ACTH
•Mobilization of fats from tissues.

6. 6
•Melanocyte stimulating effect.
•Because of structural similarity with
melanocyte stimulating hormone,ACTH
shows melanocyte stimulating effect.It
causes darkening of skin by acting on
melanophores which are the cutaneous
pigment cells containing melanin.