Thyroid function naturally peters out over time, which means less hormone production overall. But many women are diagnosed as hypothyroid during or after pregnancy. "When your thyroid function is low, skin becomes dry and scaly," explains Miami dermatologist Dr. Fredric Brandt. He also notes that the epidermis starts losing moisturizing hyaluronic acid when you hit your late 20s. Since estrogen enhances hyaluronic acid production, declining estrogen levels mean less moisture. Kaplan describes the result: "Your skin becomes leathery and starts to crack like an old raincoat. The purpose of skin is to act like a barrier. As your face gets drier, it also gets more sensitive." The good news is that you can replenish hyaluronic acid topically. Sealing in serums with a cream will protect against irritation and further moisture loss.
Estrogen is stored in fat, so severe dieters will look older, faster, warns Fields. Aside from hyaluronic acid production, estrogen also affects collagen and elastin levels. And hormonal dips thin the skin, making it less pliable and more prone to wrinkling. "After age 30, you're losing 1 percent of your collagen a year," says Fields. "Peptides, growth factors, and retinols will help rebuild the collagen, but elastin is difficult to replace." Elastin is responsible for—you guessed it—elasticity, so skin becomes looser and less flexible over time. "Facial wrinkles occur when the skin becomes too big for the tissue underneath," explains Kaplan. The first place you'll start seeing fine lines is around the eyes (the periorbital region), where skin is the thinnest. When peptide-fortified eye and face creams are no longer enough, Kaplan recommends lasers and injectable fillers to plump out the padding.
In the decade leading up to menopause, testosterone finally drops as much as estrogen. You'll see less acne, but the deepest layers of your skin will start to thin and sag. Also, early hormone-related bone loss collapses facial structure, squaring off formerly rounded eye sockets (causing dark circles under the eyes) and increasing skin slackening. Going on and off the Pill makes things worse, warns Fields: "Skin looks more juicy when you're on the Pill, but if you're playing around with it, your face will get dehydrated and drop earlier." However, topical applications of plant-derived estrogens (phytoestrogens like soy, green tea, and wild yam) are safe and can help firm up the face. "If you start applying phytoestrogens in your 40s," says Boston dermatologist Dr. Ranella Hirsch, "I'd bet money that it would help prevent much of the sagging that occurs after menopause."