What workup do you recommend for pediatric patients with telogen effluvium?

If the onset was relatively recent, and there is a history of a known trigger, such as a significant illness (e.g., high fever, surgery, other physical trauma) or other stressful life events, I don't usually do any workup right away. I recommend giving it at least 2-3 months to see if it starts to stabilize and turn around. Similarly, if the parent says it happened and the hair is already growing back in, I don't usually do any workup. I just ask them to return if it does not continue to improve and return to its former fullness. If the parent says the problem has been ongoing for months, with no signs of improvement, and/or they report other potentially concerning physical symptoms (e.g., unusual fatigue, pallor, etc.), I will check thyroid labs and get a CBC and iron panel with serum ferritin to check for thyroid disease and/or iron deficiency anemia, as both of these can cause a chronic telogen effluvium picture in children.