Could taking thyroid glandular effect a woman's menstrual cycle negatively in the beginning? I experience a heavier and longer period this time. I got my period 2 1/2 weeks into taking 1/2 grain thyroid which I increased to 1 grain at the two week mark. I feel fine other than that, my temps have gone up some and my heart rate too. Could it be increased adrenalin sensitivity shifting the estrogen:progesterone balance towards estrogen?