TABLE 4.

Impact of pubertal hormones on factors that predispose to syncope events.

Factors predisposing orthostatic intolerance	Pubertal hormones that exacerbate	Pubertal hormones that ameliorate
Vasodilatation	Estrogen	Progesterone (by inhibiting action of estrogen)
	Progesterone	Melatonin (by inhibiting action of estrogen)
	Growth hormone
	IGF-1
	Insulin
	Thyroid hormones
Impaired vasoconstriction	Insulin	Leptin
	Progesterone
Hypotension	Estrogen	Cortisol
	Growth hormone
	IGF-1
Low sympathetic activity	Progesterone	Leptin
		Insulin
Excessive venous pooling	Insulin
Hypovolemia	Estrogen	Cortisol
		Progesterone
Hypocapnia	Estrogen
	Progesterone
Decreased cerebral blood flow	Estrogen and progesterone (via hypocapnia)	Estrogen
Excessive tachycardia	Insulin	Progesterone
	Leptin
	Thyroid hormones
Decreased baroreflex sensitivity	Progesterone	Estrogen

IGF-1, insulin-like growth factor-1.