Age-related alterations of pituitary-thyroid function in normal female subjects and in female patients with simple goitre.

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Age-related alterations in pituitary-thyroid function were studied in 173 female patients with simple goitre and in 70 normal female subjects. They were divided into 4 groups according to age: A group, less than 19 years; B group, 20 to 29 years; C group, 30 to 39 years; D group, 40 to 59 years. Serum triiodothyronine (T3) concentrations decreased progressively but insignificantly with age in female patients with simple goitre and in normal female subjects, whereas serum thyroxine (T4) concentrations remained constant throughout the studied age range. Only in female patients with simple goitre, did basal serum TSH concentrations show a tendency to increase with age. However, thyrotrophin-releasing hormone (TRH)-stimulated increase of serum TSH was progressively augmented with age both in female patients with simple goitre and in normal female subjects; the magnitude of change was greater in the former group. As reflected by acute increases of serum T3 and T4 concentrations, thyroidal responsiveness to endogenous TSH was progressively depressed with age in female patients with simple goitre and in normal female subjects. This age-related thyroidal refractoriness to TSH was more apparent when the changes were expressed as delta T3 (stimulated T3 - basal T3)/delta TSH (maximum TSH after TRH - basal TSH), and delta T4 (stimulated T4 - basal T4)/delta TSH. Delta T4/delta TSH was lower in female patients with simple goitre than in normal female subjects in all age groups. However, the difference was significant only for delta T4/delta TSH in group A. Thyroidal responsiveness to exogenous TSH also gradually declined with age in female patients with simple goitre.(ABSTRACT TRUNCATED AT 250 WORDS)