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Telogen Effluvium

Authors: Ayaa Alkhaleefa Telogen effluvium (TE): Causes, pathophysiology, and clinical findings Reviewers: Elise Hansen, Sunawer Aujla, Dr. Jori Hardin* *MD at time of publication Telogen effluvium: non-scarring alopecia characterized by diffuse shedding of telogen-phase hair due to a reactive process Hypothyroidism ↓ Thyroid hormones (T3,T4) ↓ Binding of thyroid hormone to receptors in the skin and hair Cell division ceases in keratinocytes The catagen phase of the hair cycle is triggered (involuting phase where hair enters apoptosis) Delayed re-entry of telogen (resting) hair into the anagen (growing) phase Post-partum hair loss (telogen gravidarum) ↑ Circulating placental estrogen Prolonged anagen phase ↑ Hair growth during pregnancy Baby is delivered ↓ Estrogen and other trophic hormones postpartum The increased amount of anagen hairs from pregnancy all enter catagen phase simultaneously Nutritional deficiencies i.e. iron deficiency Critical illness Fever triggers various pro- inflammatory cytokines (tumor necrosis factor, interleukin 1b, interleukin 6, and interferon types 1 and 2) Premature entry into catagen phase (the body induces cell-cycle arrest in all non-essential structures) Hair follicle keratinocytes undergo apoptosis in response to inflammation Ribonucleotide reductase (an enzyme involved in DNA synthesis) cannot utilize iron as a co-factor ↓Iron stores ↓ Expression of iron- dependent genes (CDC2, NDRG1, ALAD, and RRM2) ↓ Expression of matrix genes of a healthy hair follicle (Decorin and DCT) ↓ Production of matrix keratinocytes (cells that form the hair shaft of growing hair) Arrest of matrix proliferation Hair shedding commonly occurs in the bitemporal areas 2-3 months after triggering event Hair shaft Hair follicle Telogen phase Skin Epidermis Dermal- Anagen phase Epidermal Junction Dermis Catagen phase Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published May 10, 2023 on www.thecalgaryguide.com