According to the Cleveland Clinic, the prevalence of true hypothyroidism (Alberto incorrectly uses the term "incidence" -- actually he writes this as "incident") in the general U.S. population is less than 1 in 300.
Going only by the results of blood testing in the absence of symptoms ("biochemical hypothyroidism"), this rises to about 1 in 22.
http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/endocrinology/hypothyroidism-and-hyperthyroidism/
So when Alberto notes that "only" 5 out of 55 (or 1 in every 11) NOP athletes have been diagnosed with the condition since joining the program -- seeming to imply strongly that others brought a diagnosis into the game with them -- I'm not sure what the "only" is supposed to mean.
0.3% of the population is clinically hypothyroid.
4.6% of the population is hypothyroid by serum analysis.
At least 9.1% of NOP runners carry the diagnosis of hypothyroidism.\
This should come as no surprise given how the NOP's own endocrinologist, the aforementioned Dr. Jeffrey Brown, deviates from his peers when it comes to establishing a diagnosis of hypthyroidism.
https://www.sciencebasedmedicine.org/is-thyroid-replacement-a-performance-enhancing-drug/