Most, if not all, autoimmune conditions appear associated with the HLA (human leukocyte antigen) region. Even if you inherit a genetic predisposition the autoimmune disease will not occur unless there is an environmental trigger. Several trigger suspects include viruses, bacteria, diet, toxins, radiation, metal, estrogen, and chronic infections.
Hashimoto's thyroiditis is seen with the HLA DR3 and HLA DR 5 gene. I have Hashimoto's thyroiditis, autoimmune pernicious anaemia (HLA DR5 gene) and non segmental vitiligo (possible abnormalities in the HLA D region genes).
The following info is from the book "The Everything Guide To Thyroid Disease" by Theodore C. Friedman, MD, PhD and Winnie Yu Scherer...
"Although the majority of people with Hashimoto's will not develop any other disorders, it's important to know what some of these autoimmune conditions are in case you do start to experience symptoms. Keep in mind, too, that you may be more likely to develop Hashimoto's if you have one of these other conditions.
Type 1 diabetes
Pernicious Anaemia
Addison's Disease
Vitiligo
Celiac Disease
Alopecia Areta
Systematic Lupus Erthematosus (SLE)
Rheumatoid Arthritis
Sjogren's Syndrome
Inflammatory Bowel Disease
Multiple Sclerosis (MS)"
Your doctor really should be testing FREE T3 and FREE T4 and basing your meds adjustments on those, rather than TSH. However, if your TSH is "just barely normal", then, yes, you most likely need an increase. Is she testing FT3 and FT4, too? TSH range is much too high at most labs. 0.3-3.0 was recommended by AACE many years ago. Few doctors and labs use that range.
Yes, most likely Hashi's...
No causal relationship has been established between Hashi's and other AI diseases, but we do know that once you have one AI, you are more likely to get more than the general population is to get its first.