Table 1.

Circulating sex hormone concentrations across menstrual phases in healthy women and POTS patients

	Early follicular phase						Mid-luteal phase
	Healthy			POTS			Healthy			POTS
	E2	P	E2/P	E2	P	E2/P	E2	P	E2/P	E2	P	E2/P
Mean	32.4	0.93	42.7	32.4	0.82	50.3	91.8*	11.1*	12.6*	82.6*	7.9*	31.6
SD	8.9	0.50	23.2	8.7	0.50	21.9	46.7	5.7	13.3	41.5	6.0	45.8

Hormones measured via blood draw on testing days. E₂, oestradiol (pg mL^–1); P, progesterone (ng mL^–1); E₂/P, oestradiol to progesterone ratio (arbitary units). Data for healthy women are from a previous study (Fu et al. 2009).

^*Significant difference from the EF phase in the same group (P < 0.05).