If Your Hair Seems Thinner, You’re Probably Not Imagining It. Here’s Why.

Whether you experience pattern baldness or just notice your hair isn’t quite as thick as it used to be, most of us (regardless of gender!) will experience some sort of hair thinning as we age ― and it can start earlier than you thought.
We checked with top doctors and a biologist to get to the bottom of why our hair thins and what determines when this happens.
Several factors determine how much hair we have and whether we have a thick, full head of hair or thin, wispy strands. However, the primary factor is genetics, explained Dr. Paradi Mirmirani, a dermatologist at Kaiser Permanente in Vallejo, California.
How much hair you start with, and whether it is thick or thin, depends on how many hair follicles you were born with and the diameter of the follicles.
“We are born with a certain number of hair follicles on our head,” which determines how much hair we have, she said. How thick or thin each strand grows to be is determined by the diameter of the hair follicle, explained Dr. Zafer Çetinkaya, a hair transplant surgeon with EsteNove in Turkey. Bigger follicles produce thicker hair, while smaller follicles result in thin strands.
“Genetics also determines the shape and color of the hair that is produced by each hair follicle,” Mirmirani added.
However, genetics is just the start. Other factors can influence how much hair each individual grows and even its color and shape. One of the most important factors is nutrition. You “can’t make a hair with full fidelity if you don’t have all the necessary building materials,” Mirmirani explained. According to Mirmirani, medications and chronic illnesses can also impact how much and what type of hair you grow.
No matter how much hair you start with, it is bound to thin as you age. “The process is called hair miniaturization,” Mirmirani said.
Ben Greulich, an assistant professor of biology at Mercer University who teaches classes related to cell biology and genetics, explained: “Some follicles will eventually stop producing hair,” he said. “Those individual hairs that do remain may become thinner as well.”
“As the hair follicle shrinks in size over time, it produces a smaller, finer, shorter hair fiber, which does not cover the scalp as well,” Mirmirani added.
This typically occurs at three or four different points in life, due to changes in hormones and age-related functions.
First, although many people may believe that hair thinning starts in old age, it may begin much earlier. “In some cases, it can begin as soon as puberty,” Mirmirani said.
“The surge in androgen hormones” that occurs during puberty for men “can lead to hair miniaturization in genetically susceptible individuals” when they are teenagers or throughout their 20s and 30s, she explained.
Second, changes in hormones in our 40s and 50s can also lead to hair thinning. In women, estrogen decreases during menopause, which can “lead to changes in hair diameter and texture,” Mirmirani said.
For men, continuous exposure to the androgen hormones they begin producing in puberty, including testosterone and dihydrotestosterone (DHT), leads to changes in hair growth and quality over time. By age 50, 30-50% of men have lost some hair and develop a condition called male androgenetic alopecia.
Third, other age-related changes, “including a decrease in vascular and metabolic functions that are necessary for optimal hair production,” occur as we grow older as well, Mirmirani said. This typically occurs in our 60s, she said.
Finally, hormone fluctuation that affects your hair can also occur during pregnancy and the postpartum period, Çetinkaya said.
According to Greulich, “Pregnant women experience very high levels of estrogens, and typically have increased hair growth until estrogen levels plummet following the birth of the baby. This sudden and sharp decline in estrogen has been associated with post-partum hair loss,” similar to hair loss that may occur after menopause.
For most people, thinning hair is just a normal part of aging and isn’t anything to be concerned about. Normal changes in hair growth and quality are “slow and gradual,” Mirmirani said.
However, “sudden changes in the hair may reflect an underlying health condition,” so it’s important to check with your doctor if you notice an abrupt change, she cautioned.
For example, hormonal imbalances such as thyroid problems, nutritional deficiencies such as a lack of iron, zinc or vitamin D, autoimmune diseases and stress may lead to premature or sudden hair loss, Çetinkaya explained.
According to Çetinkaya, “The process of hair thinning due to age or hormonal factors tends to be progressive. It doesn’t necessarily ‘end,’ but it can plateau as follicles shrink to a point where new hair growth is no longer possible,” he explained. The extent varies widely among individuals.
Because hair thinning is usually due to genetics, those who are genetically predisposed won’t be able to stop the process entirely, Mirmirani explained. However, there may be some things you can do to “slow the process,” she said.
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If you are concerned about hair thinning, Mirmirani recommends reducing stress, avoiding harsh hair treatments like heat styling or chemical exposure, and maintaining a healthy diet rich in vitamins and minerals, including biotin, vitamin D and iron.
For those who want to take additional steps, other options are available. However, Mirmirani cautions that “while these treatments can help, their effectiveness can vary, and early intervention generally produces the best results.”
You could consider prescription medications like minoxidil or finasteride to promote hair growth, hair transplant procedures, or platelet-rich plasma therapy to stimulate hair growth. Mirmirani adds that new research shows that stem cell treatment may be effective in dramatically increasing hair thickness and that low-level laser therapy is being studied as a treatment as well.
Always seek the help of a board-certified dermatologist before considering any treatment.