Subclinical hypothyroidism is defined biochemically as an elevated serum thyroid-stimulating hormone (TSH) and a normal serum-free thyroxine (T4) level. Some patients with subclinical hypothyroidism may have vague, nonspecific symptoms. 

Although virtually all experts recommend treatment of subclinical hypothyroidism when serum TSH concentrations are ≥10 mU/L, treatment of patients with TSH values between the upper reference limit and 9.9 mU/L remains controversial, particularly in older patients who are more likely to have complications from unintended overtreatment.

In a randomized trial evaluating the effect of levothyroxine versus placebo on quality of life measures in over 700 older patients (mean age 74.4 years) with mean TSH 6.4 mU/L, there was no difference in hypothyroid symptoms or tiredness scores after one year [2].

We do not routinely treat older patients with TSH between the upper reference limit and 9.9 mU/L.

Referrence.

1. Stott DJ, Rodondi N, Kearney PM, et al. Thyroid Hormone Therapy for Older Adults with Subclinical Hypothyroidism. N Engl J Med 2017.