Patient information: Is my hair loss because of my thyroid problem ?

Created on : #jan2025

Author: Dr. Om J Lakhani

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Corresponding notes for doctors : Hypothyroidism and Hair loss

Understanding Hair Loss and Thyroid Issues

What is Telogen?

• Telogen is the resting phase of the hair growth cycle. During this phase, hair stops growing and eventually falls out.

What is Telogen Effluvium?

• Telogen effluvium is a common cause of hair loss, usually temporary.
• It happens when the body experiences stress, illness, or major changes, causing hair to enter the resting phase and stop growing temporarily.
• If this phase lasts too long, noticeable hair loss occurs. However, hair usually grows back once the underlying issue is resolved.
• Thyroid problems, like hypothyroidism or hyperthyroidism, can also cause this type of hair loss.

Does Hypothyroidism or Hyperthyroidism Cause Hair Loss?

• Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) can lead to hair loss.

What Does Hair Loss Look Like in Thyroid Disorders?

• Hair loss is usually diffuse, meaning it happens all over the scalp rather than in specific patches.

Types of Hair Loss in Hypothyroidism

• A study found the following patterns of hair loss in people with hypothyroidism:
  • Diffuse hair loss (most common, 70%)
  • Alopecia areata (sudden patchy hair loss, 11%)
  • Androgenetic alopecia (pattern hair loss, 14%)
  • Other rare types like cicatricial alopecia, alopecia totalis, and alopecia universalis (complete hair loss).

Does Mild Hypothyroidism Cause Hair Loss?

• No, mild hypothyroidism (subclinical hypothyroidism) is unlikely to cause hair loss. This is a common misconception.

Does Hair Loss Worsen After Starting Thyroid Treatment?

• Yes, hair loss may temporarily worsen when starting treatment for hypothyroidism.
• This happens because the hair follicles become active again and shed old hair. New, healthy hair will grow back over time.

Does Radioactive Iodine Therapy Cause Hair Loss?

• No, radioactive iodine therapy (used for Graves' disease) does not cause hair loss.

Do Antithyroid Drugs Cause Hair Loss?

• Yes, some antithyroid drugs like Carbimazole and PTU can cause hair loss.

What is Alopecia Areata?

• Alopecia areata is a condition where hair falls out in round patches. It’s more common in children.
• It’s thought to be an autoimmune condition, and there may be a link with hypothyroidism, which is also often autoimmune.

Does Treating Hypothyroidism Help Alopecia Areata?

• Alopecia areata usually follows its own course, but treating hypothyroidism with levothyroxine may help improve hair loss caused by telogen effluvium.

How to Tell the Difference Between Alopecia Areata and Thyroid-Related Hair Loss?

• Alopecia areata causes patchy hair loss, while thyroid-related hair loss is more diffuse (all over the scalp).

Does Hypothyroidism Cause Hair Loss in Other Areas?

• Yes, hypothyroidism can cause hair loss in other areas, like the eyebrows and body hair.
• A classic sign of hypothyroidism is madarosis, which is the loss of eyelashes or eyebrows, though this is rare.

What is Madarosis?

• Madarosis is the loss of eyelashes (ciliary madarosis) or eyebrows (superciliary madarosis).

Do Hair Supplements Affect Thyroid Function?

• Yes, some hair supplements can affect thyroid function:
  1. Iodine: Some supplements contain iodine, which can cause thyroid problems.
  2. Biotin: This vitamin, often found in hair supplements, can interfere with thyroid function tests.

How Common is Biotin in Endocrine Tests?

• At least 50% of endocrine tests use biotin in their testing process.

Can Biotin Cause False Test Results?

• Yes, biotin can cause:
  • False low results for hormones like TSH, FSH, and prolactin.
  • False high results for hormones like T3, T4, and steroid hormones.

Clinical Pearl:

• Biotin can cause false results that might lead to a wrong diagnosis of Graves' disease (a type of hyperthyroidism).

Where is High-Dose Biotin Used?

• Dermatology: For hair and nail health.
• Neurology: For conditions like multiple sclerosis.

How Much Biotin Causes Test Interference?

• Doses of more than 5 mg/day can interfere with lab tests.

How Long Should You Stop Biotin Before Testing?

• Stop taking biotin for at least 2-3 days before testing. For people with kidney problems, a longer period may be needed.

How Can Labs Check for Biotin Interference?

• Labs can use streptavidin beads or other methods to detect biotin interference.

What Else Can Cause Test Interference Like Biotin?

• The presence of streptavidin antibodies can cause similar test interference.

Do Parathyroid Conditions Cause Hair Loss?

• Yes, parathyroid conditions can also lead to hair loss.

Does Central Hypothyroidism Cause Hair Loss?

• Yes, central hypothyroidism (a rare type of hypothyroidism) can cause hair loss, especially androgenetic alopecia in women.

Other Skin Issues Linked to Hypothyroidism:

• Vitiligo (loss of skin color in patches).
• Urticaria (hives or rashes).

Key Takeaways:

• Hair loss can be caused by thyroid problems, stress, or illness.
• Treating the underlying thyroid issue often helps improve hair loss.
• Be cautious with hair supplements containing iodine or biotin, as they can affect thyroid function and lab tests.
• If you’re experiencing hair loss, consult a doctor to check for thyroid or other health issues.