Aberrations in serum proteins and thyroid size in Nigerians on the Jos Plateau and their relation to thyrometabolic function

Abstract

Controlled serum protein and thyroid function studies were carried out among 208 African patients with endemic goitre. The changes seen in the scrum protein constituents were studied and evaluated in relation to thyroid hormone levels, goitre grade and the clinical state of the patient. Mean scrum TBG and thyroglobulin values rose sharply in the early phase of goitre and remained elevated throughout. Although the mean serum total T4 was statistically and significantly higher in endemic goitre compared with the normal subjects (/ » 3.72. P = 0.005), the free thyroxine index was significantly lower and scrum T4 fell progressively (r = 0.975) with increasing thyroid grade. In contrast, mean serum T3 rose continuously (r *= 0.910) but appeared inflated due to a proportionate increase in TBG in several cases, giving a misleading picture of T3 — thyrotoxicosis in otherwise clinically normal subjects. An increase in T3/T4 ratio and consequently in thyroid function therefore occurs with advancing thyroid size. Inconsistent binding of T4 to TBG causes wide variations in thyroxine index. Mean serum albumin and betalipoprotein appeared inversely related to thyroid function. These changes imply that in order to evaluate a patient with endemic goitre accurately a detailed biochemical investigation of the thyroid may be necessary.