TRH and hypothyroidism: Moncayo et al [28] reported that in the evaluation of 2570 TRH stimulation tests in subjects with normal basal TSH level, exaggerated TRH stimulation tests were found in 5.4% for TSH below 2.0 mIU/L, 30.2% for TSH between 2.0 and 3.0 mIU/L, 65.5% for TSH between 3.0 and 3.5 mIU/L, and 87.5% for TSH between 3.5 and 4.0 mU/L, suggesting latent hypothyroidism was present in normal basal TSH levels and proposed gray area values between 3.0 and 3.5 mIU/L.