Thyroid, Iron and Other Medical Causes of Hair Loss

Hair loss is sometimes a sign that something else in the body needs attention. An underactive or overactive thyroid, low iron stores, hormonal shifts, certain medications and some skin and autoimmune conditions can all thin the hair. When one of these is behind the problem, treating the underlying cause is the first and most important step, and cosmetic hair treatments are secondary at most.

This article explains the common medical causes, the blood tests your family doctor may consider, and how a medical work-up fits with any hair restoration plan.

Why the body sheds hair when something is off

Each hair follicle cycles through a growing phase, a short transition phase and a resting phase before the hair falls out and a new one starts. Hair follicles are among the most active tissues in the body, so they are sensitive to changes in hormones, nutrients and overall health.

When the body is under strain, more follicles can shift into the resting phase at once. A few months later, those hairs shed together. This is why medically driven hair loss often shows up as diffuse thinning across the whole scalp rather than a receding hairline or a single bald patch. The delay between the trigger and the shedding can make the connection easy to miss.

Thyroid conditions

The thyroid gland in the neck makes hormones that help regulate metabolism, including the activity of hair follicles. Both hypothyroidism (too little hormone) and hyperthyroidism (too much) can lead to thinning hair.

Other clues may include tiredness, feeling cold or hot when others are comfortable, weight changes, changes in bowel habits, a racing or slow heartbeat, or dry skin. Some people have few symptoms besides the hair change. Hair usually begins to recover once thyroid levels are brought back into a healthy range, though regrowth takes months, and the process can be gradual.

Iron and other nutrients

Low iron is a frequently discussed contributor to hair shedding, particularly in people who menstruate, are pregnant or recently gave birth, follow a restricted diet, or have conditions that affect absorption or cause blood loss. Iron stores are usually checked with a ferritin test, sometimes along with a complete blood count.

The exact ferritin level needed for healthy hair is debated, and research on whether raising iron improves hair in people who are not truly deficient is mixed. What is clear is that iron deficiency itself deserves a medical explanation, because the reason for it matters to your overall health.

Other nutritional factors that may be considered include:

• Protein and overall calories, especially after rapid weight loss or a very restrictive diet
• Vitamin D, which is often low during Nova Scotia winters, though its role in hair loss is not fully understood
• Zinc and vitamin B12, in people at higher risk of deficiency

It is worth knowing that taking high doses of some supplements without a deficiency can cause problems of its own. Too much vitamin A or selenium, for example, can actually contribute to hair loss. Biotin supplements can interfere with some laboratory tests, including thyroid tests, so tell your doctor if you take them.

Hormones, medications and other conditions

Several other medical factors can affect the hair:

• Hormonal conditions such as polycystic ovary syndrome, which can bring irregular periods, acne or extra facial hair along with scalp thinning
• Life stages such as the months after childbirth or the transition through menopause
• Medications, including some used for blood pressure, mood, seizures, blood clotting, acne and cancer, as well as starting or stopping hormonal birth control
• Autoimmune and inflammatory conditions, including lupus and alopecia areata
• Scalp conditions such as psoriasis, fungal infection or scarring forms of hair loss
• Major physical stress, such as surgery, a high fever or a serious illness

If you suspect a medication is affecting your hair, please do not stop it on your own. Talk to the doctor who prescribed it. There are often alternatives, and stopping some medications suddenly can be dangerous.

Shedding linked to illness or stress is covered in more detail in our article on telogen effluvium.

Blood tests your doctor may order

There is no single standard panel for everyone. Your family doctor will choose tests based on your history, symptoms and examination. Common options include:

• Thyroid-stimulating hormone (TSH), sometimes with other thyroid hormones
• Ferritin and a complete blood count
• Vitamin D or B12 in selected people
• Hormone levels when there are signs of excess androgens or irregular cycles
• Tests for autoimmune disease when other symptoms point that way

Many people with pattern hair loss have entirely normal blood work, and that is useful information too. It helps confirm the diagnosis and avoids treating a problem that is not there. In some cases, a referral to a dermatologist or a scalp biopsy may be needed, especially if there is redness, scaling, pain or shiny patches that suggest scarring.

Where hair restoration treatment fits in

Treatments such as platelet-rich plasma (PRP) or medications for pattern hair loss are not a substitute for correcting a thyroid problem or iron deficiency. If a medical cause is driving the shedding, cosmetic treatment is unlikely to help much until that cause is managed, and some people find their hair recovers well enough that no further treatment is needed.

It is also common for more than one factor to be present. Someone may have a genetic tendency toward pattern thinning that becomes more noticeable after a period of low iron or a thyroid change. In that situation, a physician can help sort out which parts are likely to improve on their own and which may benefit from targeted treatment. An overview of the broader picture is in our guide to the most common causes of hair loss.

At HealthPark Medical Aesthetics, a hair consultation includes a medical history and a look at any recent blood work. If tests have not been done, we may suggest you see your family doctor first.

When to see your doctor promptly

Book an appointment with your family doctor if hair loss is sudden or heavy, if it comes with other new symptoms such as fatigue, weight change, palpitations or irregular periods, or if the scalp is painful, red or scaly. Patchy loss with smooth bald spots, or loss of eyebrows and eyelashes, also deserves assessment.

Frequently asked questions

Will my hair grow back once my thyroid is treated?

Many people see improvement once thyroid levels are stable, but it is gradual. Because hair grows slowly, it can take several months before shedding settles and a year or more for density to fill in. Results vary from person to person.

Should I take iron pills just in case?

Not without testing. Iron supplements can cause stomach upset and constipation, and too much iron can be harmful. A simple blood test can show whether you actually need it, and your doctor can look for the reason if your levels are low.

Do I need blood tests if my hair loss runs in the family?

Not always. A clear family pattern with typical features may not need extensive testing. However, if anything about your history or symptoms is unusual, your doctor may still check a few basic tests before you start treatment.

If you are noticing thinning and are unsure where to start, a consultation can help you understand the possible causes, what has already been ruled out, and whether any treatment makes sense now or after a medical check-up. We are happy to work alongside your family doctor.