HORMONES HAVE VARIABLE IN VIVO �STABILITY�
HORMONE
OXYTOCIN
ACTH
CORTISOL
FSH
LH
ADH
INSULIN
60 min
70 min
5-8 min
3-5 min
8 min
3h
I5 min
ALDOSTERONE
t½
70 min
POTENTIAL REASONS
FOR
VARIABLE STABILITY
HORMONE
FORMS COMPLEX WITH
BINDING
PROTEIN WHICH PROTECTS
IT
FROM DEGRADATION
HORMONE
CLEAVED BY SPECIFIC
PEPTIDASES
IN PLASMA
SHORT
PEPTIDES ARE PARTICULARLY
VULNERABLE TO DEGRADATION
BECAUSE THERE ARE
FEW
CONSTRAINTS ON THEIR CONFORMATION
STEROIDS
ARE HYDROPHOBIC
AND
MAY PARTITION INTO
MEMBRANES AND ADIPOSE TISSUE