Abstract: An electronic system for non-invasive monitoring of estrogen of a female human comprises a wearable device (1) and a processor (13, 30, 40). The wearable device (1) includes a first sensor system (101) configured to be worn in contact with the skin of the female human and to determine a level of perfusion of the female human. The processor (13, 30, 40) is configured to receive and store the level of perfusion of the female human from the first sensor system (101) for a respective point in time. The processor (13, 30, 40) is further configured to determine a change in the level of perfusion of the female human, using the levels of perfusion of the female human stored for a plurality of respective points in time. Furthermore, the processor (13, 30, 40) is configured to detect a change in estrogen level of the female human based on the change in the level of perfusion of the female human.