Circannual Variations of Plasma Thyrotropin in Klinefelter’s Syndrome

Abstract

The aim of this study was to explore the occurrence of abnormalities in the circannual thyrotropin (TSH) rhythm in Klinefelter’s syndrome (KS). For 3 years, 69 healthy adult males and 73 patients with KS, usually living in Sardinia, were studied by a cross-sectional design. Plasma samples were taken between 08.00 and 09.00 h and TSH was radioimmunoassayed. First, the mean (± SD) of the data, grouped for each month of the year, was estimated to seek any macroscopic annual variation. Then, a cosine function was fitted to the single serially independent data by the single cosinor method in order to test for any statistically significant rhythm and, if the no-rhythm assumption is rejected, to describe the circannual parameters. Our patients showed circannual mean TSH concentrations lower than controls (p < 0.001) without any statistically significant circannual rhythm, which was instead apparent in normal subjects with the annual crest time in December (95% CL November–February). Our results support the hypothesis that in KS the impaired TSH secretion may be related to abnormalities in the hypothalamic-pituitary coordination of the circannual rhythmicity of this hormone.

Chronothyroidology: Chronobiological Aspects in Thyroid Function and Diseases

“…The occurrence of any circannual rhythm was statistically investigated by the cosinor method. Healthy adults showed a significant circannual TSH rhythm with acrophase in December, as previously observed in prepubertal boys, while patients with Klinefelter’s syndrome showed circannual mean TSH levels significantly lower than controls without any statistically significant circannual TSH rhythm [ 68 ]. We concluded that, in this syndrome, an abnormality in hypothalamic–pituitary coordination impairing TSH release could also involve circannual periodicity of this hormone and, thus, with respect to clinical implications, the treatment of patients with this syndrome should be also aimed at restoring the lost circannual rhythmicity [ 68 ].…”

“…Healthy adults showed a significant circannual TSH rhythm with acrophase in December, as previously observed in prepubertal boys, while patients with Klinefelter’s syndrome showed circannual mean TSH levels significantly lower than controls without any statistically significant circannual TSH rhythm [ 68 ]. We concluded that, in this syndrome, an abnormality in hypothalamic–pituitary coordination impairing TSH release could also involve circannual periodicity of this hormone and, thus, with respect to clinical implications, the treatment of patients with this syndrome should be also aimed at restoring the lost circannual rhythmicity [ 68 ]. A circannual rhythm of TSH with the same characteristics found in our prepubertal and adult healthy subjects has recently been confirmed in Japanese people with the highest concentrations in winter, disengaged from thyroid hormone variations but inversely related to seasonal variations in environmental temperature [ 69 ].…”

“…In the subsequent years, we studied whether the occurrence of a circannual TSH rhythm was present also in healthy adult men and whether the genetic and hormonal alterations occurring in Klinefelter’s syndrome were responsible for abnormalities of this rhythm in affected patients [ 68 ]. For this purpose, we had been investigating for 3 years the monthly TSH variations in 73 patients affected by Klinefelter’s syndrome and 69 healthy adult males, matched for age and weight.…”

“…( B ) Single cosinor display of circannual variations in these hormone concentrations and their characteristics, visualized by polar cosinor plot. A significant rhythm was validated only for TSH, as revealed by its ellipse (continuous tract), which does not cover the pole (zero: center), and with acrophase in December, as indicated by the arrow starting from the center and directed towards December (confidence limits October–February) [ 68 ].…”

Circannual Oscillations of Function Compared with Morphometric Changes in the Thyroid Gland of the Wistar-Rat

“…Other works (Jordan et al, 1983) described moderately high TSII blood levels in November and lower in April, or high from November till March and lower from April till June (Wong et al, 1979). At the human, lower TSH blood levels were found from July till August and high in January (Bellastella et al, 1986).…”