Why Is My Part Getting Wider? Understanding Hair Thinning in Women

Why does the part widen with female pattern hair loss?

A widening part is the hallmark presentation of female pattern hair loss (FPHL), also called androgenetic alopecia in women. In FPHL, hair follicles at the central and crown scalp gradually miniaturize under the influence of androgens and genetic predisposition — each successive hair that grows is finer, shorter, and less pigmented than the one before it. Because the density at the center scalp decreases while the frontal hairline is typically preserved, the part appears to grow wider 1Ref 1Ioannides D, Lazaridou E (2015).Female pattern hair loss.Female pattern hair loss causes gradual follicle miniaturization at the central scalp; widening part with preserved frontal hairline is the characteristic pattern.

FPHL is common: it affects an estimated 12% of women by age 30 and more than 50% of women over 70. It tends to accelerate during perimenopause and after menopause, when declining estrogen reduces a natural buffering effect on androgen-sensitive follicles 7Ref 7Faubion SS, Crandall CJ, Davis L, El Khoudary SR, Hodis HN, Lobo RA, Maki PM, Manson JE, Pinkerton JV, Santoro NF, Shifren JL, Shufelt CL, Thurston RC, Wolfman W (2022).The 2022 Hormone Therapy Position Statement of The North American Menopause Society.Perimenopause and declining estrogen accelerate female pattern hair loss; hormonal management options exist and differ by menopausal status. The condition is not a reflection of poor health — it has a strong genetic component and is not caused by anything you did.

What else can make the part look wider?

Several other conditions produce diffuse central thinning that widens the part, and they can coexist with FPHL:

Telogen effluvium — a stress-triggered shed in which a large proportion of follicles shift prematurely into the resting phase. Classic triggers include significant emotional or physical stress, major illness, surgery, rapid weight loss, nutritional deficiency, or childbirth (postpartum hair loss). Shedding typically starts two to four months after the trigger and may last several months before reversing 2Ref 2Rebora A (2019).Telogen effluvium: a comprehensive review.Telogen effluvium triggered by stressors causes diffuse shedding typically starting two to four months after the trigger, visible at the part.

Iron deficiency — low ferritin is one of the most common and underrecognized reversible causes of diffuse hair loss in women, particularly those with heavy menstrual periods or dietary restrictions. Ferritin levels in the lower half of the normal range can affect hair, even in the absence of frank anemia 4Ref 4Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Thyroid dysfunction is a common and treatable cause of diffuse hair thinning in women; thyroid testing is standard in any hair loss evaluation 5Ref 5Leung AKC, Lam JM, Wong AHC, Hon KL, Li X (2024).Iron Deficiency Anemia: An Updated Review.Low ferritin is a common underrecognized cause of hair loss in women, especially those with heavy menstrual periods.

Thyroid disease — both hypothyroidism and hyperthyroidism cause diffuse telogen effluvium. A widening part alongside fatigue, weight change, or temperature sensitivity makes thyroid testing worthwhile 4Ref 4Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Thyroid dysfunction is a common and treatable cause of diffuse hair thinning in women; thyroid testing is standard in any hair loss evaluation.

PCOS and androgen excess — in women with polycystic ovary syndrome, elevated androgens can accelerate follicle miniaturization at the central scalp in a pattern resembling FPHL, often accompanied by irregular periods or acne 6Ref 6American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 194: Polycystic Ovary Syndrome.PCOS-related androgen excess is a cause of scalp hair thinning in women and is evaluated via hormonal panel.

What will a clinician look for?

A dermatologist will examine your scalp with dermoscopy to look for the pattern of hair shaft diameter variability and follicle miniaturization that characterizes FPHL, and to distinguish it from telogen effluvium and scarring conditions 1Ref 1Ioannides D, Lazaridou E (2015).Female pattern hair loss.Female pattern hair loss causes gradual follicle miniaturization at the central scalp; widening part with preserved frontal hairline is the characteristic pattern.

Blood tests are a standard part of the workup for diffuse hair loss in women and typically include TSH, ferritin and complete blood count, and (when clinically indicated) androgens such as free testosterone and DHEA-S 4Ref 4Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Thyroid dysfunction is a common and treatable cause of diffuse hair thinning in women; thyroid testing is standard in any hair loss evaluation. Hormonal testing is especially important when there are other signs of androgen excess or when PCOS is being considered 6Ref 6American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 194: Polycystic Ovary Syndrome.PCOS-related androgen excess is a cause of scalp hair thinning in women and is evaluated via hormonal panel.

If perimenopausal or postmenopausal symptoms are prominent, the clinician may also consider whether the hormonal transition is accelerating hair loss and whether hormonal options are relevant for the whole picture 7Ref 7Faubion SS, Crandall CJ, Davis L, El Khoudary SR, Hodis HN, Lobo RA, Maki PM, Manson JE, Pinkerton JV, Santoro NF, Shifren JL, Shufelt CL, Thurston RC, Wolfman W (2022).The 2022 Hormone Therapy Position Statement of The North American Menopause Society.Perimenopause and declining estrogen accelerate female pattern hair loss; hormonal management options exist and differ by menopausal status.

What treatment options are available?

The most established treatment for female pattern hair loss is topical minoxidil, applied directly to the scalp. A systematic review and meta-analysis of randomized controlled trials found that topical minoxidil 2% and 5% both significantly increase hair count in women with androgenetic alopecia compared to placebo, with 5% providing greater efficacy 3Ref 3Adil A, Godwin M (2017).The effectiveness of treatments for androgenetic alopecia: A systematic review and meta-analysis.Topical minoxidil is the most established treatment for female pattern hair loss, most effective when started before extensive thinning. It works best when started before extensive miniaturization has occurred, and requires sustained use to maintain results.

Low-level laser (light) therapy has emerging evidence as an adjunct approach for some patients. Platelet-rich plasma (PRP) injections have also been studied as an adjunct to other treatments — a meta-analysis of randomized controlled trials found PRP significantly increased hair density and thickness compared to control in androgenetic alopecia 8Ref 8Zhang X, Ji Y, Zhou M, Zhou X, Xie Y, Zeng X, Shao F, Zhang C (2023).Platelet-Rich Plasma for Androgenetic Alopecia: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.PRP injections are used as an adjunct procedure for androgenetic alopecia with supporting evidence.

If a reversible cause is found — low iron, thyroid disease, or PCOS — correcting that cause should be the first step, since it may reduce or reverse the shedding. For menopausal women, the role of systemic or topical hormonal options can be discussed with a clinician, weighing the overall benefit-risk profile 7Ref 7Faubion SS, Crandall CJ, Davis L, El Khoudary SR, Hodis HN, Lobo RA, Maki PM, Manson JE, Pinkerton JV, Santoro NF, Shifren JL, Shufelt CL, Thurston RC, Wolfman W (2022).The 2022 Hormone Therapy Position Statement of The North American Menopause Society.Perimenopause and declining estrogen accelerate female pattern hair loss; hormonal management options exist and differ by menopausal status.

A dermatologist or endocrinologist can help determine the right combination of treatments based on the specific causes contributing to your hair thinning.