First of all, thyroid hormones are actively taken up into cells and accumulate there. Therefore, the apparent volume of distribution for T4 is 10 liters rather than 5 liters (1). Secondly, I would assume a slightly lower proportion of free T4 (0.02%) (1). That results in 90 pmol/L.
This is still above the reference range for FT4. However, T4 is rapidly converted to T3, rT3, 3,5-T2, thyronamines and iodothyroacetates (2). In combination, these mechanisms end up in plausible concentrations.
This scenario also explains, why even slight variations of parameters can end up in dramatic changes of hormone concentrations, e.g. in allostatic load (3).
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Hoermann R, Midgley JE, Larisch R, Dietrich JW. Homeostatic Control of the
Thyroid-Pituitary Axis: Perspectives for Diagnosis and Treatment. Front
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Chatzitomaris A, Hoermann R, Midgley JE, Hering S, Urban A, Dietrich B, Abood
A, Klein HH, Dietrich JW. Thyroid Allostasis-Adaptive Responses of Thyrotropic
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Front Endocrinol (Lausanne). 2017 Jul 20;8:163. doi 10.3389/fendo.2017.00163. PMID 28775711