Hair loss is a symptom, not a single condition. It has several distinct causes — genetic, hormonal, nutritional, metabolic — that frequently overlap. This matters practically: the appropriate treatment depends on which cause or causes are present. This guide explains how to distinguish them.
Reviewed by Dr. David Oliak, board-certified surgeon
Updated August 2026
Hair is not essential to survival, so the follicles are among the first structures the body downregulates when something upstream is disrupted: a nutritional deficiency, a hormonal shift, elevated inflammation, or metabolic strain.
This makes hair a useful indicator. A change in the hair is often the visible sign of a process occurring at the level of cellular health.
Treating the hair without identifying that process addresses the symptom while the cause continues. Our approach begins with the cause: we determine why the hair is changing, because that determines which treatment will be effective.
The most common cause of hair loss is androgenetic hair loss: the pattern loss that runs in families, driven over years by the effect of DHT (a derivative of testosterone) on genetically susceptible follicles. It is often called male- or female-pattern hair loss, but it affects both sexes.
In men it typically recedes at the temples and thins at the crown. In women it usually appears as a widening part and diffuse thinning across the top, rather than a receding hairline.
The mechanism is miniaturization: susceptible follicles shrink with each growth cycle, producing progressively finer, shorter hairs until they no longer produce a visible hair. It is gradual and progressive if untreated.
The follicle remains viable for a long period on this path, which is the window in which treatment is effective. This is the cause most therapies address, from prescription medications that reduce DHT's effect to in-office treatments that deliver growth factors to the follicle.
A different pattern, diffuse shedding across the scalp rather than in a defined area, is usually telogen effluvium. A stress pushes an unusually large share of follicles into their resting phase at once, and those hairs shed together a few months later.
The triggers are well recognized: serious illness or fever, surgery, childbirth, a period of high stress, a crash diet, or rapid weight loss, including the shedding some people see on a GLP-1 medication.
The follicles are not lost, and the hair regrows once the trigger resolves. The shedding appears two to four months after the trigger, which is why it can seem unexplained.
If the shedding is sudden and diffuse rather than a slowly widening pattern, this is the likely cause, and it usually resolves on its own. Rapid weight loss as a trigger is covered in detail on our [hair loss after weight loss] page.
Between those two lies a set of contributors that are common, treatable, and frequently overlooked, because a short visit examines the hair rather than the body producing it. Three are most important.
Nutritional gaps. Hair is built from protein and is among the first tissues affected when protein intake is low, common on a restrictive diet or when appetite is reduced. Low iron, measured as ferritin rather than a basic blood count, is one of the most common and most missed drivers of thinning, particularly in women. Low vitamin D and zinc also contribute. These are simple to test and correct, and doing so often improves the response to other treatments.
Thyroid and hormonal changes. Both underactive and overactive thyroid can cause diffuse shedding, and thyroid disease is common and easily tested. In women, the hormonal changes of perimenopause and menopause, falling estrogen and a shifting balance with androgens, frequently unmask or accelerate pattern thinning; PCOS does the same through androgen excess. In men, hormonal health contributes to pattern loss as well.
Metabolic and inflammatory strain. This is the layer most often missed. Insulin resistance, chronic inflammation, and poor metabolic health impair the follicle's environment and blood supply and worsen pattern hair loss. Addressing them treats the conditions under which hair grows, which is where a root-cause approach applies.
The most common error is treating hair loss as a single problem with a single solution. In most people two or three causes are present at once — a genetic pattern progressing alongside low ferritin, a thyroid change, or a metabolic problem.
Selecting a treatment without identifying which causes are present is how patients spend a year on a therapy that was never suited to their condition. We establish the cause first.
A focused set of labs usually identifies what is driving the loss, and often part of the answer is something ordinary and correctable that had not been checked. Hair is an indicator of health, and treating the cause and the hair together produces durable results.
— Dr. David Oliak, board-certified physician and surgeon
Some thinning with age is normal: follicles slow, hairs grow finer, and density decreases. But "it is just age" is where a large amount of treatable hair loss is dismissed.
Aging rarely acts alone. It is often the point at which a lifelong genetic susceptibility becomes apparent, or at which a nutritional or metabolic change that has been developing becomes visible.
Whether age contributes matters less than what else contributes, because the other factors are the ones that can be treated.
Once the cause is established, the treatment is specific rather than empirical. A genetic pattern responds to therapies that reduce DHT's effect and to treatments that deliver growth factors and nutrients to the follicle.
A nutritional or thyroid cause responds to correcting the deficiency or the thyroid abnormality. A metabolic cause responds to improving metabolic health.
Most plans address more than one cause, because most patients have more than one, and layering the appropriate treatments is more effective than any single agent.
There is also a delivery constraint: actives applied to the surface of the scalp reach the follicle in very low amounts. This is why the treatments that work deliver actives locally to the follicle, and why our in-office care is built around personalized, multimodal plans anchored on a delivery treatment.
We cover the methods and compare the options on our [Alma TED] and [treatment comparison] pages.
Women are frequently told that thinning hair is stress or age and are sent away without a workup. That is where the treatable causes are found — low ferritin, a thyroid change, the metabolic changes of menopause — and identifying them changes the outcome.
Understanding the cause and beginning treatment are not mutually exclusive; we do both in the same plan. The purpose of identifying the cause is not to delay treatment but to ensure the treatment selected is the one the patient's hair loss will respond to.
— Dr. David Oliak, board-certified physician and surgeon
If your hair is changing, the most useful step is to identify the cause rather than guess.
For a gradual pattern, treatment is most effective when started early, while the follicles remain active. For sudden diffuse shedding, it is worth confirming the trigger and checking for treatable causes rather than waiting.
If the underlying drivers — iron, thyroid, metabolic health — warrant assessment, that is the purpose of our evaluation. The treatment plan then follows the cause.
Let's begin
The appropriate treatment for hair loss depends on the cause, so that is where we begin. A hair consultation is complimentary and reviews your treatment options, including Alma TED.
If the underlying drivers warrant a closer look — iron, thyroid, metabolic health — our Comprehensive Evaluation assesses the full picture. To speak with us first, call 714-671-2005.
Alma TED: how we deliver actives to the follicle
PRP vs. Alma TED vs. microneedling: the delivery routes compared
Hair loss after weight loss
Women's hair loss: what's different and why
Losing hair in your 30s or 40s: a guide for men
The clearest indicator is the pattern. Sudden, diffuse shedding that began a few months after an illness, a stressful period, childbirth, or rapid weight loss is usually telogen effluvium. It is temporary and regrows.
A slow, gradual thinning in a defined pattern — a receding hairline or crown in men, a widening part in women — is more likely genetic. It is progressive if untreated but very treatable, especially early. Many people have both. An examination and a few labs distinguish them.
The same core causes as in men — most commonly a genetic pattern. But women more often have treatable contributors in addition: low iron (ferritin), thyroid changes, the hormonal shifts of perimenopause and menopause, and conditions such as PCOS.
Women's pattern loss also appears differently, as diffuse thinning and a widening part rather than a receding line. A proper workup matters, because these contributors are easily missed.
Yes, and it is common. Low iron measured as ferritin, low protein intake, and low vitamin D or zinc all contribute to thinning, and they are frequently missed because a standard visit examines the hair rather than testing the body.
These are simple to check and correct, and doing so often improves the response to other treatments.
Yes. Both underactive and overactive thyroid can cause diffuse shedding, and thyroid disease is common and easily tested. Metabolic problems — insulin resistance, chronic inflammation, poor metabolic health — impair the follicle's environment and worsen pattern loss. These are among the root causes a comprehensive evaluation is designed to identify.
Some treatments can be started without testing, and for a clear genetic pattern that is often reasonable. But because most people have more than one cause, testing prevents months spent on a treatment aimed at the wrong problem.
At minimum, checking iron, thyroid, and metabolic markers is worthwhile when hair loss is significant. It is inexpensive and frequently identifies something correctable.
With a complimentary hair consultation, in which we examine the pattern, take a history, and review treatment options including Alma TED. If the underlying drivers warrant a closer look, we direct you to our Comprehensive Evaluation. It assesses iron, thyroid, hormonal, and metabolic health together.
