Hi Nas!
I developed melasma due to MHT. I was referred to a dermatologist. I use a custom compounded cream, a modified Kligman formula containing hydroquinone, tretinoin, hydrocortisone, ascorbic acid. Sunscreen is a must and I never leave the house without it. Light and heat are triggers, as are any irritants that cause inflammation. I had to bin skincare and makeup products containing fragrance and other irritants. Sadly, it was the most expensive products that led to the most irritation, especially when my skin was sensitive and adjusting to the HQ/tretinoin.
Hydroquinone is not used on a continuous basis. When I'm not using the HQ, I use tretinoin and skincare containing vitamin C, niacinamide, etc. There are a lot of products targeting pigmentation.
The melasma has faded considerably, but not disappeared entirely. It looks like light freckling and it's not obvious. I'm satisfied with the results. It will likely start darkening again by the end of summer and I'll start another cycle of HQ.
Melasma can be stubborn. If you haven't requested a referral to a dermatologist, I suggest you do so. It can take so long to see a specialist these days.
Hope you've been well and the Mirena is settling.