Drugs that cause hair loss
Drugs can cause telogen hair loss that starts about 12 weeks after starting the drug and continues while on the drug.10 Dosing changes can also precipitate hair shedding.7 Any medication or over-the-counter product the patient is taking should be suspected in hair loss.
Drugs known to cause telogen effluvium are oral contraceptive pills, androgens, retinoids, beta-blockers, angiotensin-converting enzyme inhibitors, anticonvulsants, antidepressants, and the anticoagulants heparin and warfarin (Coumadin).10,14 Changing or stopping any oral contraceptive can precipitate telogen hair shedding.10,14 Oral contraceptives containing an androgenic progestin and hormonal replacement therapy with high-dose progesterone can cause telogen hair shedding with or without patterned alopecia.7,11,14
IDENTIFYING THE TRIGGERS
Normal hair shedding usually goes unnoticed. However, at the onset of telogen effluvium, hair shedding increases by 25%.7
To determine the true trigger of telogen hair loss, the relationship between the trigger and the hair loss must be reproducible, with improvement of the hair shedding following correction of or removal of the trigger, and deterioration on rechallenge.3
In acute telogen effluvium, ie, the acute onset of telogen hair loss 2 to 3 months after an acute, short-lived triggering event,4 a detailed history is important to determine an accurate timeline. No trigger can be identified in some cases.2 Regrowth is not visible for 4 to 6 months.7 If the trigger is identified and removed, recovery can be expected to be complete.4,7
In chronic diffuse telogen hair loss, ie, telogen hair loss lasting more than 6 months,3,14 a range of triggers can precipitate the hair loss. It can be due to idiopathic chronic telogen effluvium. It can also be secondary to prolonged, sequential, or repeated triggers, such as a nutritional deficiency or underlying systemic disorder, and shedding can be less pronounced than in acute telogen effluvium.7
Chronic telogen effluvium is an idiopathic condition with telogen hair shedding lasting longer than 6 months, and with a fluctuating chronic course over many years without an identifiable trigger.16,17 These patients can present with a full head of hair or with bitemporal recession and no widening of the midline part.16,17 Histologic study shows no miniaturization of the hair follicles.17 The diagnosis of chronic telogen effluvium is made by the exclusion of causes of diffuse telogen hair loss, including androgenetic alopecia.
Androgenetic alopecia typically presents as well-defined, patterned scalp hair loss in patients with a family history of androgenetic alopecia. Diffuse hair loss over the vertex and widening of the central part in women, with or without frontal accentuation (“Christmastree” pattern), is characteristic.14,18
The functional mechanism of patterned hair loss is related to a shortening of the anagen phase and a progressive miniaturization of the hair follicles.18 In some instances, androgenetic alopecia may present as diffuse scalp hair loss with episodic increases in telogen hair shedding.8,14 This presentation can be mistaken for other causes of diffuse telogen hair loss.14
Although, most women with patterned hair loss have normal androgen levels,14 androgen excess disorders such as polycystic ovarian syndrome can cause diffuse scalp hair loss or patterned hair loss.7,18 Laboratory testing can exclude other causes of telogen hair loss, and an androgen screen should be performed in women who present with signs of androgen excess, such as irregular menstrual periods, hirsutism, or acne.18 Scalp biopsy can confirm the diagnosis of androgenetic alopecia. 14
ANAGEN HAIR LOSS: KEY FEATURES
Anagen hair loss, the result of interruption of the anagen hair cycle, presents as abrupt anagen hair shedding with a severe diffuse scalp alopecia.9 A serious insult to the hair follicles can cause up to an 80% loss of scalp hair.7 The time course for anagen effluvium is usually rapid compared with telogen effluvium, occurring within days to weeks of the insult to the hair follicles.9 The hair-pull test (see below) is positive for dystrophic anagen hairs with tapered ends.9 If the insult ceases, hair growth restarts again within weeks.
Causes of anagen effluvium include cancer therapies and alopecia areata
Antimitotic chemotherapeutic agents induce arrest of the anagen phase and present a toxic insult to the rapidly dividing hair matrix.9 Hair loss usually begins 1 to 2 weeks after chemotherapy is started and is most noticeable by 1 to 2 months.19 The scalp hair is usually most affected, but all body hair including eyelashes and eyebrows can be affected.10
Other triggers of anagen hair loss include radiation,9 heavy-metal poisoning, and boric acid poisoning.19 Radiation has also been known to cause telogen hair loss and permanent hair loss.9,10
Alopecia areata is another cause of anagen hair shedding.9 This autoimmune condition of the hair20 can cause patchy hair loss, complete hair loss of the scalp (alopecia totalis), or complete loss of scalp and body hair (alopecia universalis).
THE IMPORTANCE OF THE HISTORY IN IDENTIFYING TRIGGERS
The history should concentrate especially on events in the 3 months before the start of the hair loss in the case of telogen hair loss. A history of recent illness or surgery should be recorded. A dietary history is also helpful.21 A detailed drug history including new medications or over-the-counter supplements should be recorded, as should any change in dosages.
As mentioned above, other important factors include recent chemotherapy or radiation therapy, a family history of pattern hair loss such as androgenetic alopecia, oral contraceptive use, and hormone replacement therapy.