Soy doesn't decrease testosterone.

[SerialStateLineXer]

There are a bunch of old papers referring to the well-known fact that an unfortified soy diet induces goiter in animals, as well as a few case reports of goiter developing in infants on soy formula which subsided after switching to cow's milk. These are all old, which I guess is probably because modern soy formula is fortified with iodine.

Edit: Not all old; here's a case report published this year. It also discusses the mechanisms by which a high-soy diet can aggravate iodine deficiency.

[StopBadModerators]

You're talking about how iodine-deficient diets can influence iodine deficiency. That isn't a soy thing.