Are these thyroid conditions not genetic, as medicine describes, but rather passed on to offspring during gestation or through virus in breast milk, and then persist in the system, even life-long in some cases?

Both vectors of viral transmission can take place, and that will get the virus going early in the young, and perhaps increase the chance of having long-term problems. But the virus can be transmitted from person to person as well and can be introduced directly into a person by extraterrestrials making a site visit, while the victim sleeps, to expose them. So the family of Epstein-Barr viruses is endemic in human culture and quite common, often leading to serious or even devastating consequences that are still unappreciated by medical science, who largely consider it as a source of acute viral infection that can become prolonged but will eventually subside, not appreciating that it can be a lifelong resident within the body causing repeated and varied problems that might come and go but be quite serious.