What is the #1/most important hormone for the human body to sustain life?

This, of course, could be argued. Insulin may be the most important
hormone for sustaining one's own life. For sustaining the propogation
of life, gonadotropin releasing hormone may be the most important (for
developing sex glands).

Any Hormone leading to metabolism is important for sustaining life.
The adrenal cortex contains three layers that make steroid hormones,
which are derived from cholesterol. The thickest or middle layer, the
zona fasciculata, makes another life-sustaining group of hormones, the
glucocorticoids. The major glucocorticoid is cortisol
(hydrocortisone). Good Luck! -Amin

Oxytocin is sometimes called the hormone of love, so it gets my vote!

Thanx everyone for your help.