Estradiol cyclicity might contribute to the alterations in plasma GH1 protein levels across the menstrual cycle.

A recent study identified 198 proteins whose levels in the plasma change across the menstrual cycle in women of reproductive age; one of which is GH1 (Growth Hormone 1). Both plasma GH1 and estradiol levels first peak during the same phases of the menstrual cycle (late follicular phase). Previous reports also showed that GH1 expression (both mRNA and protein) is upregulated by estradiol. Based on these observations, we here hypothesize that circulating estradiol levels might be responsible, at least to a certain extent, from the changes in GH1 protein levels in the plasma during the menstrual cycle in women of reproductive age. Considering the importance of GH1 in the female reproductive system, this potential estradiol-regulated changes in GH1 protein levels in the circulation during the menstrual cycle need to be better understood.