telogen effluvium

Last reviewed 01/2018

Normally, eight to ten percent of scalp hairs are in the resting - telogen - phase of the hair cycle. Telogen effluvium describes the premature entry of follicles into the resting phase resulting in shedding of hair from these follicles 6-10 weeks later (1). It is a generalised, non - scarring alopecia.

• average normal scalp has 100 000 hairs, with approximately 90% of these normally in anagen (growing) and 10% in telogen
  • average normal daily hair fall-out is 100 telogen (resting) hairs. With telogen effluvium, the anagen:telogen ratio is shifted to 70% anagen, 30% telogen, with average daily shedding of 300 hairs

Characteristically, the shaft of the shed hair has a "club" at the root.

• telogen effluvium occurs when an increased number of hairs enter the telogen (resting) phase of the hair cycle from the anagen (growing) phase, and these hairs are lost approximately 10 weeks later
  • usually, an average of 100 hairs are lost each day, but this becomes significantly more in telogen effluvium, in which 30 to 50 percent of body hair can be lost
  • may be precipitated by severe illness, injury, infection, surgery, crash diets, psychological stress, giving birth, thyroid disorders, iron deficiency, anemia, or drugs. Hyperthyroidism and hypothyroidism can cause telogen effluvium, which is usually reversible when the thyroid status is corrected (except in long-standing hypothyroidism)
  • severe iron deficiency anemia may be associated with it, but this remains controversial
  • drugs that cause telogen effluvium include antithyroid agents, hormones, anticonvulsants, anticoagulants, beta blockers, angiotensin-converting enzyme inhibitors, and lithium. No cause is found in approximately one third of cases (2,3)
  • usually presents with an increased number of hairs in their hairbrush or shower, and sometimes thinning of the hair in the scalp, axillary, and pubic areas. A detailed history may indicate the cause of the hair loss, which usually has occurred two or three months before the hair falls out
    • on examination, there is generalized hair loss with a positive hair pull test, indicating active hair shedding, particularly at the vertex and scalp margin.

The condition is associated with (1):

• recent acute illness
• surgery
• bulimia and anorexia nervosa
• blood loss
• shock
• severe stress
• iron deficiency
• hypothyroidism
• the use of beta blockers

It often follows 4-9 months after pregnancy when the level of oestrogen falls (1).

Reference:

• Sheretz EF et al. Skin reactions to systemic disease. Medicine International 1992;102: 4278-81.
• Shapiro J, Wiseman M, Lui H. Practical management of hair loss. Can Fam Physician. 2000 Jul;46:1469-77
• Mounsey AL, Reed SW.Diagnosing and Treating Hair Loss. Am Fam Physician. 2009 Aug 15;80(4):356-362.