Endocrine Abstracts

Background/Aim: Impact of age on hypothalamic –pituitary –thyroid axis, interesting from theoretical and practical aspects, have been studied. Our aim was to find out: correlation between T3 (triiodothyronine) and T4 (thyroxine) hormone level and old age, so as of other, for thyroid function relevant parameters: TSH (thyroid stimulate hormone), TRH (thyreothropin releasing hormone) test, thyroid ultrasonography, thyroid gland scintigraphy with ¹³¹ J, ¹³¹J fixation test, thyroid antibodies and thyroglobulin.

Methods: Study included 125 subjects, divided in four groups, according to the age: control group (from 20 to 40 years); group A (from 41 to 50 years); group B (from 51 to 60 years) and group C (from 61 to 70 years), as well as into subgroups according to the sex. All patients were established total and free hormones T3, T4, TSH and test with TRH; thyroid gland scintigraphy with ¹³¹ J, ¹³¹ J fixation tests, thyroid antibodies and thyroglobulin. All hormone analyses, thyroglobulin and thyroid antibodies were determined by radioimmunoassay (RIA). Thyroid scinitgraphy was done with ¹³¹ J and ¹³¹ J fixation test was monitored 4, 24 and 48 h after 1.85 MBq test dose applied perorally.

Results: There was a significant decrase in levels with aging of both total and free T4, and, somewhat, minor fall of both total and free T3 in men, in contrast to mild level rise of total T4 and T3 in women, but within the range of eutyroidisam, with no alternations in free hormone levels. A significant fall of thyroglobulin antibodies with aging was observed in the group of males and a considerable increase of thyroglobulin was shown in the group of females. Old age and sex dont’ have impact on radio jodine fixation persentage in thyroid gland, thyroid scintigraphy and throid gland echostructure.

Conclusion: Hypothalamic-pituitary –thyroid axis is presereved with aging. The determination of the values of the free T4 should be basic test at older persons. Evident drop in thyroid hormone levels with aging can be considered as adaptation of the organism to reduce requrements for energy, thys representing a significant metabolic parameter of biologic aging process. A normal range of thyroid hormone values shoud be modified for the persons older than 70. These physiological variation should be standardised in the interpretation of the tests of the thyroid function.