Hair Loss in Women: The Most Common Drivers

I have talked with so many women in midlife who are struggling with hair loss and I’ve had my own journey as well. Hair loss is one of those symptoms that feels personal fast. It can mess with your confidence, your routines, and honestly, your willingness to look in the mirror some days so I wanted to talk about it. 

To help you navigate the complexities of thinning and regrowth, this is the first post in a 2-part series dedicated to helping you understand the science and the solution.

• Part 1: The simplified hair-growth cycle + the most common root causes of hair loss (and how they overlap)

• Part 2: My personal hair loss journey: what I noticed, what labs I looked at, and how I fixed it
  

The hair growth cycle simplified 

Your hair doesn’t constantly grow; it goes through phases. Here’s what you need to know: 

1) Growth phase (Anagen)

This is when the hair follicle is actively producing hair. Most of your hair is here most of the time.

2) Transition phase (Catagen)

A short “pause” phase where the follicle shrinks and stops growing. 

3) Resting/shedding phase (Telogen)

The follicle rests and eventually sheds the hair. It’s important to note that we shed hair daily. Up to 100 hairs per day is often considered within the normal range. 

Key point: A lot of hair loss isn’t your hair “breaking.” It’s more often your body pushing more follicles into the resting/shedding phase. That’s why hair loss often shows up 2–4 months after a stressful event, illness, major diet change, surgery, travel, postpartum, etc. 

What tends to alert us that something’s up: 

• a noticeable increase in shedding (especially in the shower or brush)

• a widening part or visible scalp where you didn’t see it before

• a ponytail that feels thinner over time (or suddenly)

Shedding vs. Thinning-What’s the difference? 

Not all hair loss looks the same. We can have diffuse shedding (often telogen effluvium)

where you’re losing more hair than usual across the whole scalp. It’s commonly triggered by a stressor (environmental, emotional, dietary, or other health related issue, etc.) and often shows up months after the trigger.

The other thing that can happen is pattern thinning (often female pattern hair loss).  This is more about gradual thinning, often at the crown/top of the head or a widening part. It can often be influenced by hormone shifts and follicle sensitivity.

It’s important to note that these can overlap. You can have a stress-triggered shed on top of hormone-related thinning. 

The big idea: hair loss is rarely one thing. Isn’t that fun? 

Hair loss is usually multi-factorial.

It can be:

• Stress changes your hormones and appetite, disrupts sleep, and depletes nutrients

• Hormone shifts can affect thyroid signaling and nutrient needs

• Low thyroid output can slow growth and increase shedding

• Nutrient issues can make the follicle more fragile 

So yes, you can have a “main driver,” but most people have multiple contributing factors.

So now that we know about the phases of hair growth, and that the by the time it shows up, typically we’ve been dealing with an issue for some time, let’s talk about the most common causes of hair loss and what to look for. 

1) Micronutrient issues (low OR high)

Hair is not essential for survival even though for many of us it’s an important part of who we are. Unfortunately, if our bodies are under-resourced, it will prioritize other systems first at the expense of our hair health. 

Common nutrient players:

• Iron status: This includes ferritin (and yes, it can be too low or too high)

  • Contributing factors are often Heavy menstrual cycles

  • Pregnancy or postpartum periods

  • Low calorie diets

  • Low intake of red meat or other iron-rich foods

• Zinc- Low Zinc levels can lead to hair thinning, slowed hair growth, and increased shedding. Zinc is also involved in androgen metabolism, which may influence hair loss patterns in individuals with elevated androgen levels.

• Biotin (B7)-You will see this in almost any supplement marketed for hair health, when the truth is biotin deficiency is pretty rare. We do sometimes see this with very restrictive diets, long-term antibiotic use, and other gut issues involving malabsorption.

• Vitamin D-Vitamin D plays an important role in hair follicle cycling, and low levels have been associated with several forms of hair thinning. Our hair follicles have vitamin D receptors, and when we have adequate vitamin D, it helps to support the transition from resting back to the growth phase.

• B12 and folate-These B vitamins contribute to hair health through red blood cell production and cellular energy metabolism. Deficiencies in these vitamins may impair oxygen delivery and cell turnover, which can affect tissues like hair follicles. This is especially important in individuals who follow vegan diets without proper supplementation, have gut absorption issues, or have autoimmune digestive conditions.

• Selenium-Selenium is very supportive of thyroid hormone metabolism. Because thyroid hormone strongly influences hair growth, not getting enough selenium may contribute to hair thinning, but on the flip side, excessive intake of selenium can also negatively affect hair health.

• Omega 3 Fatty Acids-Omega-3s support scalp skin health, inflammatory balance, and cell membrane health. Low intake of omega-3s can contribute to dry scalp, increased inflammation, and poor hair quality.

• Protein intake -Protein is not a micronutrient but one of the most important foundational factors for hair growth. Hair is primarily made of keratin, which is a type of protein. Because of this, getting enough protein is essential for maintaining normal hair growth and follicle function. Hair follicles are actually some of the most metabolically active tissues in the body, so they require a steady supply of amino acids to support keratin production and follicle growth. When we aren't getting enough protein, the body prioritizes the amino acids for more critical functions, not for hair growth.
  

An important note: You’ll often see articles about hair loss that list a handful of nutrients and immediately suggest supplements. While these nutrients absolutely play important roles in hair growth, it’s important to zoom out and look at the bigger picture.

Hair loss is rarely caused by a single nutrient in isolation. More often it reflects a broader issue so supplementing blindly isn’t always the best approach. In some cases, taking high doses of micronutrients without understanding your individual needs can actually create new imbalances or make existing issues worse.

In coaching, we start with the fundamentals and then use lab work and individual context to determine what specific nutrient support may actually be needed.

2) Stress (including “good stress”)

Stress isn’t just emotional. Our bodies experience stress in lots of different ways including under or overeating, poor sleep (quality and/or quantity), travel, illness, over training, big life changes, chronic inflammation, and many other potential health challenges. 

Stress can cause hair loss through cortisol signaling, blood sugar instability, digestion or absorption issues, nutrient depletion, or pushing follicles into the telogen phase. 

3) Hormone shifts

This is a big one for women in their late 30s through 50s.

Key hormones involved include estrogen and progesterone, which help regulate the balance between growth and shedding phases, as well as androgens (testosterone and DHT sensitivity) and insulin, which can affect follicle health and hair thinning patterns.

This becomes especially relevant during perimenopause, the transitional years leading up to menopause, when hormone levels begin to fluctuate more significantly. During this time, estrogen and progesterone levels can become more variable and gradually decline, which may shorten the hair growth phase and increase the proportion of hairs entering the shedding phase. At the same time, some women may notice increased sensitivity to androgens, which can contribute to thinning around the crown or widening of the part line. These hormonal shifts are a common reason hair changes become more noticeable in the late 30s, 40s, and early 50s.

This doesn’t automatically mean you need HRT or a prescription. It means we should consider timing, symptoms, and labs when appropriate. 

4) Thyroid Function

Thyroid hormones help regulate metabolic rate and influence how quickly cells grow and turn over in the body, including the cells within hair follicles. When your thyroid isn’t functioning properly, hair follicles may shift more quickly into the shedding phase, which can lead to thinning hair or increased hair loss over time. Hair changes are often accompanied by other symptoms that may suggest thyroid involvement, such as dry skin, constipation, feeling unusually cold, fatigue, or slower recovery from exercise or daily stressors. Hair is often just one piece of a broader pattern.

It’s also important to remember that the thyroid doesn’t operate in isolation. Thyroid hormone activity is closely connected to other factors in the body, including chronic stress, inflammation, and overall nutrient status. Nutrients such as iron, selenium, and iodine all play roles in thyroid physiology, but context matters. Both deficiencies and excesses can influence thyroid signaling, which is one reason it’s helpful to look at thyroid health within the broader picture of diet, lifestyle, and lab work rather than focusing on a single nutrient or supplement.

5. Other Common Contributors to Hair Loss

There are also several other factors that can contribute to hair shedding that are worth mentioning because they’re not uncommon and can often be overlooked.

• Postpartum hair loss: After pregnancy, hormone levels shift rapidly and many hairs that stayed in the growth phase during pregnancy move into the shedding phase. This is a normal part of the hair cycle, but the shedding can sometimes feel more dramatic when it overlaps with nutrient depletion, sleep loss, and the overall stress of the postpartum period.

• Illness: Hair shedding can also occur after illness, infections, or surgery. These types of physiological stressors can trigger a pattern called telogen effluvium, where a larger number of hair follicles enter the shedding phase at the same time.

• Certain medications may also influence hair growth and shedding patterns. Some blood pressure medications, antidepressants, acne treatments, and other drugs list hair thinning as a potential side effect.

• Autoimmune Conditions, such as alopecia areata, where the immune system targets hair follicles can cause hair loss.

• Scalp health: It’s also worth paying attention to the health of the scalp itself. Signs such as persistent itching, redness, flaking, tenderness, or unusual buildup may indicate scalp inflammation or infection that can interfere with healthy hair growth.

• Mechanical Stress: Tight hairstyles, extensions, aggressive brushing, and frequent heat styling can contribute to traction-related hair loss or breakage over time.

• Aggressive dieting or rapid weight loss: When the body experiences low energy availability, it often shifts resources away from processes like hair growth. This has become a lot more commonplace since the introduction of GLP medications. 

  
  

The point of this list isn’t to overwhelm you. It’s simply a reminder that hair loss is usually a symptom with a context, not something that one nutrient or stressful event might have caused. 

In Part 2, I’ll share my personal hair loss journey and what I did to get on the other side of it.