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