Labels:text | screenshot | black and white | black | font | document OCR: liagnostic A low T4 is common to all causes of hypothyroidism, but it is not absolutely onic because a variety of severe acute and chr rugs in illnesses, together with interference of d T4 valuesthyroid function tests, may also cause lo petitive (Fig. 15.34). Thus, low TBG levels or com ty, and binding by drugs alters the binding capa vels are total T4 levels are reduced, but free T4 le are not usually normal. Even when TBG levels duction affected, severe illness may lower T4 pro sually and T4 to T3 conversion. rT3 levels are increased, and TSH levels are normal, Ir otal T4 asymptomatic autoimmune thyroiditis, normal, levels may be towards the lower limit of but TSH levels are often mildly elevated
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