"subclinical" refers to a condition or illness that is not showing noticeable symptoms or signs, even though it may still be present in a person's body. Full definition
I just looked in PubMed (a free database of medical articles), using the search strategy «dietary treatment Hashimoto's» and came up with some interesting articles, mainly about using selenium supplementation for treatment of subclinical hypothyroidism in patients with Hashimoto's thyroiditis: (nutritionfacts.org)
Is zinc deficiency a cause of subclinical hypothyroidism in Down syndrome? (progressivehealth.com)
Our results from pooling data of all available prospective cohorts, showing increased fracture risk in subclinical hyperthyroidism with even higher risk for participants with TSH levels of less than 0.10 mIU / L, are consistent with these recommendations.» (sciencedaily.com)