Rhythmic hormone secretion appears to be a common characteristic of several endocrine systems. Alterations in these secretions are associated with the pathophysiology of certain diseases. Thyrotropin (TSH) exhibits a nocturnal surge in normal subjects. The time and the amplitude of the surge depend on the waking or the sleeping state. The TSH surge is decreased or abolished in various pathological conditions. Assessment of the surge is of particular interest for the early detection of central (pituitary) hypothyroidism, and in the exploration of isolated decreased TSH to predict further evolution toward hyperthyroidism. However, the characterization of the TSH surge needs simplification and standardization before this index could be used for the practical evaluation of thyroid function.

Adrenocortical Hyperfunction↗

PubMed1996

[Thyroid function and dysfunction in the elderly].

The consequences of aging function are appreciated in various ways. In fact most of the thyroid hormone abnormalities described in the elderly are secondary to associated disease or treatments. Health and nutritional status seem to be more determinant than age. However, there is an increased prevalence of dysthyroidism in the elderly. Symptoms may be misleading and induce severe general repercussions. Mild or occult forms of dysthyroidism characterized by abnormal TSH levels with normal free thyroid hormone levels are not uncommon. Their clinical significance and their prognosis without treatment are still unresolved. The frequency of dystrhyroidism during old age and the possibility of a specific treatment may be in favour of a screening by a systematic TSH determination in elderly patients.

Aged↗

PubMed1995

The circadian thyrotropin rhythm is delayed in regular night workers.

In order to determine whether the circadian thyrotropin (TSH) rhythm is adapted to a night-active schedule, plasma TSH and body temperature were measured for 28 h every 10-min in 8 regular night workers and in 8 day-active subjects. In night workers, the shift of 8-h in the sleep period induced a mean shift of 6 h 30 min of the TSH acrophase which remained located, as in day-active subjects, at about the time of sleep onset. The nadir of the body temperature rhythm was shifted by an equivalent amount and occurred systematically during the sleep period, so that both parameters maintained a fixed phase relationship. TSH and temperature rhythms had similar amplitudes in the two groups. However, mean TSH values in night workers returned more rapidly to basal values. These results demonstrate that, together with body temperature, TSH acrophase is adapted to regular night work, suggesting that TSH may be a good index for evaluating the orientation of the endogenous clock.

Adult↗

PubMed1995

Twenty-four-hour profiles and sleep-related variations of cortisol, thyrotropin and plasma renin activity in healthy African melanoids.

The 24-h hormone profiles have been well documented in caucasians living in a temperate climate, but they have never been examined in melanoid subjects under equatorial conditions, with a 12-h light-dark cycle in a hot climate. To establish normal data for this population, blood samples were taken at 10-min intervals over 24 h in five healthy young melanoids living in Abidjan (Ivory Coast). Cortisol and thyroid stimulating hormone (TSH) concentrations and plasma renin activity (PRA) were determined by radio-immunoassay and sleep was registered using polysomnography. Data were compared with results obtained in Strasbourg (France) from six healthy aged-matched caucasians. The 24-h profile of cortisol concentration was similar in both groups, with a 2-h phase advance in the melanoids. Nocturnal fluctuations of PRA, strongly linked to the rapid eye movement-non rapid eye movement (REM-NREM) sleep cycles, occurred in both groups, with higher levels in the caucasians in the last 2 h of sleep along with greater amounts of NREM sleep. After an evening increase in TSH, the sleep onset-related decrease seen in the caucasians was not observed in the melanoids. In both groups, increasing concentrations of TSH and cortisol occurred with awakening, decreasing concentrations being observed during slow-wave sleep. As in the caucasians studied in the temperate climates, the melanoid subjects living at the equator showed the same temporal organization of hormone rhythms within the 24-h period and the same relationships between the pulses and specific sleep stages.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Low cholesterol concentrations in free-living elderly subjects: relations with dietary intake and nutritional status.

Hypocholesterolemia has been reported in epidemiologic studies to be associated with increased mortality from noncardiovascular causes. Low cholesterol concentrations have been reported in various pathologic conditions and in institutionalized elderly patients, and seem to be associated with poor outcome. The role of nutritional factors in the genesis of hypocholesterolemia was investigated in 380 free-living elderly subjects. Subjects in the lowest cholesterol quartile had lower free triidothyronine and prealbumin concentrations and a lower Folstein's score (a minimental test) than did those in the other quartiles. They did not differ from the other subjects for energy or nutrient intakes. Only 12 subjects (9 men and 3 women) had cholesterol concentrations < 3.62 mmol/L: the men had low free triidothyronine, free thyroxine, and prealbumin concentrations but normal energy and nutrient intakes, whereas the women differed from those with normal cholesterol concentrations for biological and nutritional data. These results indicate that low cholesterol concentration is a nonspecific feature of poor health status that is independent of nutrient or energy intake. The role of nutrient factors as a determinant of cholesterol concentration appears marginal in free-living elderly subjects.

Aged↗

PubMed1994

Nycthemeral patterns of thyroid hormones and their relationships with thyrotropin variations and sleep structure.

In order to precise the relationships between TSH, FT3, and FT4 nycthemeral variations and the relationships between thyroid hormone variations and sleep, 8 healthy young males were studied twice, once during a 24-h experiment with normal nocturnal sleep, and once during a night of sleep deprivation. The subjects received continuous enteral nutrition and remained supine during the whole experiment. Blood was sampled every 10 min for TSH, FT3, and FT4 measurements. Thyroid hormones exhibited small oscillations which were not systematically related to TSH pulses, and there was no evidence of a nycthemeral rhythm. SWS was associated with TSH declining phases, whereas awakenings were strongly associated with ascending phases of TSH variations. There was no association between sleep structure or awakenings and thyroid hormones. Sleep deprivation led to increased TSH and FT3 levels, without any variation in FT4 levels. These results demonstrate that short-term thyroid hormone variations do not only depend on the effect of TSH on thyroid secretion but also on a possible role of TSH on peripheral FT4 to FT3 conversion. Conversely, the relationships between TSH and SWS or awakenings are not mediated by thyroid hormones.

Adult↗

PubMed1994

Thyroid hormone status and nutrient intake in the free-living elderly. Interest of reverse triiodothyronine assessment.

Fasting or hypercaloric diets are established methods of inducing low triiodothyronine (T3) levels that resemble the sick euthyroid syndrome in adults, but little is known on the mechanisms of this syndrome in the elderly. Decreasing T3 does not seem to be an unavoidable consequence of ageing, but the role of illness or other factors in this decline remains unclear. The aim of this work was to study the influence of nutritional factors on thyroid hormone levels in free-living elderly subjects. A 3-day dietary survey was conducted in 440 randomized subjects aged between 65 and 96. Cholesterol, apoproteins, prealbumin, hemoglobin, thyrotropin-free thyroxine (FT4), FT3 and reverse T3 (rT3) were assayed in each subject. Only 11 subjects had low FT3 levels, and they also had low levels of cholesterol, prealbumin and hemoglobin and a lower Folstein score compared to the rest of the population. Twenty-one subjects had isolated elevated rT3 levels, they were older and had significantly lower energy and fat intakes than the rest of the population. There was a clear reduction in FT3 levels and an increase in rT3 levels with age, although in the normal ranges, which occurred despite maintenance of a high-energy intake even in the oldest group. The FT3 level was lower in the subjects with poor health status, whereas high rT3 levels were associated with low energy intake in men. Stepwise regression showed that hemoglobin, age and prealbumin were the best predictors of FT3 levels, whereas age and energy intake were the main predictors of rT3 levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1994

Twenty-four-hour profiles of plasma renin activity in relation to the sleep-wake cycle.

OBJECTIVE: To evaluate the relative contribution of sleep and the endogenous circadian rhythmicity in producing the 24-h variations in the plasma renin activity. METHODS: Ten normal young men were studied, under basal conditions with normal nocturnal sleep from 2300-0700 h and once after a night of total sleep deprivation followed by 8 h daytime sleep from 0700 to 1500 h. Plasma renin activity was measured every 10 min for 24 h and the profiles were analysed using the pulse detection program ULTRA. RESULTS: During the 8 h night-time sleep a significant increase in the mean plasma renin activity levels occurred compared with the subsequent 8-h waking periods. After the shift in the sleep period, a sleep-associated increase was clearly apparent during the daytime hours. The number of the amplitude of the oscillations, linked to the non-rapid eye movement-rapid eye movement sleep cycles, increased during sleep (at whatever time it occurred), and were dependent on the regularity and the length of the sleep cycles. In awake subjects the plasma renin activity generally fluctuated in a more damped and irregular manner, but occasionally the plasma renin activity oscillated at a regular periodicity with two dominant peaks centred around 100 and 50 min. CONCLUSION: These results demonstrate that the 24-h plasma renin activity variations are not circadian in nature but are related to sleep processes, which create the nycthemeral rhythm by increasing both the frequency and the amplitude of the oscillations.

Adult↗

PubMedDate not supplied

[Hodgkin's disease with vertebral localizations. Indication for orthopedic treatment].

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Adrenal Cortex Hormones↗