Hair is thinner toward the roots. What is this?

When you notice that some of your hair is thinner toward the roots, it can be related to a disruption in the hair growth cycle, especially since you’ve been diagnosed with telogen effluvium (TE). In TE, hair prematurely enters the resting (telogen) phase, causing it to shed. The thinner roots you're seeing could be a sign of miniaturization, where the hair follicles are producing weaker or finer hair due to stress, hormonal changes, or other factors triggering TE.
As your hair recovers from TE, it’s normal to see thinner, finer hair temporarily as the follicles work to restart the growth cycle. Over time, as the growth phase stabilizes, the hairs should become thicker and more uniform from root to tip again.