High Estrogen Level Causes Melasma?

There are some reasons to believe that any alteration in the progersterone/estrogen ratio can cause or aggravate irregular pigmentation as is seen with melasma and chloasma.
Clearly, exogenous forms of estrogen are known to trigger this condition, so it would make sense that endogenously high levels may do the same.

Serum levels of estrogen do not correspond to melasma occurence, however exogenous estrogen from foods and medicine can stimulate melanocytes.  I would begin Melaquin AM and Melaquin PM for the melasma and remove any estrogen loads you may have.

Great question.
Melasma is a very common asquired dyscromia that occurs only in the sun-exposed areas . It is worsened by sun exposure, pregnancy ( where it is called chloasma or the mask of pregnancy), oral contraceptives, and certain anti-epileptic drugs like Dilantiin.
It is particularly common among Latinos and Asians. Melasma is more apparent during the summer months attesting to the role of sol.
Curiously, although estrogen has long been felt to be central to the cause of melasma, there are few studies to prove this. A perusal of the literature did not turn up an answer to your question, i.e. whether women with melasma ( or men for that matter..10% of cases are in males) have higher levels of estrogen. One can speculate, and since we do not have the research to back this up, the higher levels of estrogen AND progesterone during pregnancy and oral contraceptives DO indeed play a role
Perhaps a clue elicited in a study performed by Moy et al and published in the Journal of Drugs in Dermatology. Although a small study, they showed that estrogen receptors were upregulated in people with melasma. So perhaps, it is not the amount of estrogen but the activity at the estrogen receptor site.
There are some other interesting facts. When post-menopausal women are given estrogen replacement, they do not particularly develop melasma. Thus estrogen alone is not the cause. Interestingly, combination treatment using estrogen and progestoerone in post-menopaulsal women led to melasma in women who did not have melasma during their pregnancy.
One thought ( and this is my own speculation), perhaps, the sun turns on estrogen receptors with the help of progesterone which then activates melanocytes in pre-menopausal women but there are not enough estrogen receptors in post-menopausal women to do this.
Thank you for bringing up such a thought provoking question. I am fairly convinced that future research will provide answers. Also, by unlocking the role of estrogen receptors and finding a a drug to block these receptors the disfiurement of melasma will be controlled. In the meantime if you are pregnant or taking oral contraceptives find a good, safe sunscreen.