Most of the dark spots we develop on the face are part of an ageing process due to excessive sun exposure. They don’t appear on covered areas of our body and have a typical round brown shape.
On the other hand we have spots that are larger in size and have these margins as if the coast of Wales or Scotland in a map. They appear specially in pregnant women or at that age.
For a dermatologist it is easy to recognize that something is not working properly. 30% of these women are taking birth control pills. Many others have thyroid problems or great stress. Many more are taking medication for depression or the central nervous system.
Today we know that the hormone or molecule responsible for Melasma is synthesized in a big molecule called Proopiomelanocortin (POMC). The cells responsible for manufacturing this compound live in the basal layers of our brain, in the most primitive areas. This POMC contains inside the structure for all the other hormones that we need to stimulate our body. Let us imagine that our thyroid gland is not working properly. Our brain will have to produce more POMC inside which, a small fraction will become a hormone to stimulate the thyroid. Next to it, unfortunately, another fraction or piece will stimulate the face to produce these spots called Melasma. Any time there is a hormonal problem, we end up having Melasma.
This also explains why women, with complex cycles of fertility, ovulation, pregnancy will be more prone to develop melasma.
If a doctor sees a Melasma, he can start searching for a systemic or hormonal problem.