Estrogen has an immunomodulatory effect on the body, it tends to potentiate the immune system in women moreso than men. Statistically, women have to deal with more allergies than men, an immune response. On one hand, women can probably fight off infections better, but also develop autoimmune issues as well.
The bacterial infection theory from my perspective is enticing. It may very well be a combination of any potential bugs like fungi, virii, parasites, or autoimmune response to tagged receptors. Tricky bugs often come in multiples and set up shop to help each other out by building a community within a biofilm. Gradual migration out of the biofilm would produce a gradual immune response or at intervals.
Some of the bugs have genes that allow them to enter a latent phase where they are not active, typically enclosed in a capsule or cyst-like encasing that iodine and the immune system cannot penetrate. Some enter cells and act as parasites, feeding on cells and reproducing (HIV, for example).
Basically, when the environment is hostile for survival, some bugs can enter defense mode and protect themselves until conditions change for the better. The constant active and latent phase fluctuations could be going on numerous times throughout the days, weeks, or months to years, stuck in a stalemate by the immune system. Hence, chronic infection comes to mind along with chronic inflammatory response mediated by the immune system.
The mixture of genetic makup of different people, along with diverse disease causing agent exposure, creates a dynamic populous with multiple combinations of bugs harbored by humans. That very statement is one of the reasons why it's difficult to pinpoint what's causing problems within us all. Iodine helps, but it is not a panacea in ideal conditions.
If your mom noticed a goiter at one year old, I wonder if your thyroid size in congenital.