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Biomedical subjects

L Vanhaelst

Publications and source records attributed to L Vanhaelst.

At least 109 records · Page 6Linked to original sources
PubMed1976

Pituitary-thyroid axis reaction after myocardial infarction.

Within the first 36 hours following myocardial infarction, serum total thyroxine (T4) levels were supranormal in most cases in contrast to normal thyrotropin values. After one week, T4 levels dropped to normal while TSH values rose significantly. These findings suggest that, in the acute phase of myocardial infarction, the secretion of thyroid hormones is increased, thereby inhibiting the pituitary thyrotropes. The stimulation of thyroid secretion might be due to the high levels of blood catecholamines generally found in patients with myocardial infarction.

Aged↗
PubMed1976

Gel filtration profile of immunoreactive thyrotropin and subunits of human pituitaries.

Pituitary extracts from five patients with atrophic asymptomatic thyroiditis and from five subjects without any endocrine disease, matched for sex and age, were passed through gel filtration columns and the collected fractions were analyzed in three different radioimmunoassays (hTSH-anti-hTSH; hTSHbeta-anti-pTSH; hLHAlpha-anti-LHalpha). In the alpha subunit system, every profile showed a first peak corresponding to the elution position of the intact hTSH molecule and second peak, often more important, of free alpha chain. In the beta subunit system, a high molecular weight immunoreactive protein (big hTSHBeta) was found in seven pituitary extracts; cross-reacting intact hTSH molecule was eluted as a second peak and free Beta chain was detected in all the extracts. Free alpha chain was generally found in greater amount than free Beta. In the hTSH system, every elution pattern showed a peak of intact hTSH and another in the subunit area. In six pituitary extracts (5 thyroiditis, 1 control), a high mol wt protein was eluted (big hTSH). Its predominant presence in thyroiditis extracts seems important in view of the already described immunological heterogeneity of pituitary hTSH.

Chromatography, Gel↗
PubMed1975

Usefulness of 99mTechnetium pertechnetate in periarteritis nodosa.

Radioisotopes have a wide range of application in the clinical investigation of many organs. Muscle diseases are an exception in this expanding field. We report here a case of periateritis nodosa in which unusual scintigraphic images were obtained with 99mTc-pertechnetate. The kinetics of this isotope and the scintigraphic changes were followed during treatment and found to be useful clinical tools.

Half-Life↗
PubMed1975

Effects of oral contraceptive therapy on the circadian patterns of cortisol and thyrotropin (TSH).

The daily variation of serum cortisol and thyrotropin (TSH) has been simultaneously recorded every 30-min. in 4 women taking the same oral contraceptive containing oestrogens and progestogens and in 4 control women. The circadian rhythm of cortisol persisted under contraceptive therapy with about a 2.5 fold elevation of the mean level and amplitude of the basal rhythm. Theoretical equilibrium calculations of the circadian variations of the free, transcortin-bound and albumin-bound cortisol fractions showed that these elevations are explained qualitatively and quantitatively by an oestrogen-induced increase of the same order of the transcortin cortisol-binding sites. As a consequence of the already high saturation of transcortin in normal conditions, the magnitude of the variation of free cortisol level resulting from a burst in cortisol secretion varies with the time of day. The role of albumin as a buffer is thereby emphasized. The early morning maximum, characterizing the normal TSH daily pattern, appeared to be considerably enhanced in women under contraceptive therapy. If the circadian variations of TSH are driven by thyrotropin releasing hormone (TRH), these higher morning peaks probably reflect a higher burst of TRH secretion rather than an increased responsiveness of the pituitary to TRH secretion induced by contraceptive therapy. Finally these results do not support the hypothesis of a regulation of TSH circadian variations by an inhibiotry action of cortisol. Contraceptive therapy does not appear to play a role at the level of the central clock or on the resetting mechanism.

Adult↗
PubMed1975

Effects of glucocorticoids on pituitary hormonal responses to hypoglycemia. Inhibition of prolactin release.

The characteristics of pituitary hormonal responses to insulin-induced hypoglycemia were investigated in 16 normal men. In all subjects, levels of blood sugar fell below 35 mg/100 ml. A statistically significant increase in mean plasma levels of prolactin, ACTH, cortisol and growth hormone was observed. Prolactin levels increased in all subjects but one; individual peak values were 1.4 minus 8.4 times greater than base levels. The kinetics of prolactin, GH and ACTH responses were similar; in particular, the onset of release (25 min) of prolactin, GH and ACTH was similar. After dexamethasone administration, insulin tolerance tests wererepeated in a number of subjects using adequate amounts of insulin to achieve hypoglycemia equivalent to that obtained in the control experiments. The administration of 1 mg of dexamethasone the evening before the test suppressed basal levels of ACTH and cortisol and the ACTH-but not the cortisol-response to hypoglycemia. Both basal levels of prolactin and prolactin response to hypoglycemia were significantly lowered but growth hormone response was not modified by administration of 1 mg of dexamethasone. The administration of larger doses of dexamethasone (1 mg every 6 h for 2 days) almost completely suppressed basal levels of ACTH, cortisol and prolactin, as well as the hypoglycemia-induced release of these hormones. In contrast, the growth hormone response to hypoglycemia was only partially inhibited. These findings demonstrate that both basal secretion and hypoglycemia-induced release of prolactin, ACTH, cortisol and growth hormone are suppressible by glucocorticoids.

Adolescent↗
PubMed1975

Pituitary TSH in normal subjects and in patients with asymptomatic atrophic thyroiditis: Evidence for its immunological heterogeneity.

Biological and radioimmunological measurements of pituitary TSH concentration were performed in 22 cases of asymptomatic atrophic thyroiditis and in 18 controls. Whilst bioassay revealed the presence of a greater pituitary TSH concentration in thyroiditis cases, radioimmunoassay failed to confirm such a difference. The reason therefore seems to lie in the presence in thyroiditis pituitatries of a TSH which reacted in the bioassay but showed only a weak affinity for the anti-hTSH antiserum. The slopes of radioimmunological dilution curves of the pituitary extracts were indeed significantly lower with thyroiditis pituitaries than with controls. When the whole population sample was considered, a negative correlation existed between the ratio of biological and radioimmunological TSH determinations (B/I) and the slope of the corresponding dilution curves. Since in radioimmunoassay a low displacement slope is indicative of a weak immunological affinity of the antigen for the antiserum, this demonstrated negative correlation suggests together with a high B/I ratio, even in normal people.

Biological Assay↗
PubMed1975

Gel filtration profile of circulating immunoreactive thyrotropin and subunits of myxedematous sera.

Five sera from hypothyroid patients were passed through gel-filtration columns and the collected fractions were analyzed in three different radioimmunoassays (hTSH-anti-hTSH; hTSHbeta-anti-pTSH; hLH-alpha-anti hLHalpha). For each immunological system, cross reactions were carefully studied. In the hTSH system one main peak was observed at the elution position of the entire molecule, with variable contributions in the subunits area. In the alpha subunit system, every profile showed an asymmetric peak, corresponding roughly to the position of the entire molecule; only two sera exhibited small amounts of free alpha chain. In the beta subunit system, a high molecular weight (100,000 or more) immunoreactive protein was present in every serum. Moreover, cross-reacting intact molecule was eluted as a second peak and in four sera free beta chain was detected. The significance of the big beta subunit, detectable only in the beta assay, is not elucidated.

Aged↗