Hypothalamic-pituitary-thyroid axis status of humans during development of ageing process.

We have investigated hypothalamic-pituitary-thyroid function in four groups of healthy elderly male humans. Group A (n=18, age range 20-45 years) served as healthy younger controls, group B (n=10, age range 50-60 years), group C (n=15, age range 60-70 years) and group D (n=16, age range 70-85 years) are the subjects of this study. Groups C and D showed significantly lower T3 and thyroid-stimulating hormone (TSH), and higher T4 levels with respect to controls. Evidence for TSH circadian modulation was found in group A (control) and group B subjects. The TRH-stimulated TSH peak was reduced among all elderly subjects with respect to controls and appeared to be pronounced with the ageing process. The maximal prolactin response was also inhibited with increasing age. Our study suggest that a resetting of the pituitary threshold for the TSH feed-back suppression along with complex alterations in peripheral thyroid hormone concentrations may, in turn, develop in older people and that appeared to manifest prominently among the oldest population. Additionally, the TSH nocturnal response appeared to be impaired with increasing age indicating an alteration of hypothalamic function.