Is The White Bulb on a Fallen Hair Seen as an Thyroid or Tumor Problem?

I am attending cosmetology school and my theory teacher told the class that when u shed hair, if hair comes out and has the little white bulb on the end of the hair strand than it is an internal problem such as thyroid or tumors and if it doesnt then that means its more than likely an external problem and me and 2 of my friends have the bulb on the root of our hair strand, does that mean that we have something wrong?

It is normal to see a white bulb on a pulled hair. There is no connection to diseases or tumors and the white bulb at the end of fallen hairs. If you pull your hair (don’t make a routine of it) a few hairs will come out and some of them will have white bulbs. Hair coming out is part of the hair cycle and the hairs that come out are about to go into telogen.

Hair follicle cells have three phases of growth:

1. Growth phase (Anagen phase) which lasts anywhere from 2 to 6 years. This is the phase where your hair is actively growing at approximately 10cm per year. 85% of hair is at this phase at any given time.
2. Transitional phase (Catagen phase) which lasts about 2 weeks. This is the phase where the hair follicle shrinks and prepares to enter the resting phase.
3. Resting phase (Telogen phase) which lasts about 1-6 months. This is the phase where hair does not grow, but stays attached to the follicle. Some hairs are shed at this phase, but at the end the hair follicle re-enters the growth phase to start the cycle over again. 10-15% of hairs are at this phase at any given time.