Raoul Leclercq

SIMULTANEOUS STUDY OF CORTISOL, GROWTH HORMONE AND PROLACTIN NYCTOHEMERAL VARIATIONS IN NORMAL AND OBESE SUBJECTS. INFLUENCE OF PROLONGED FASTING IN OBESITY

Hourly integrated concentrations (IC) of growth hormone (GH), prolactin (PRL) and cortisol were determined by a continuous sampling procedure in six obese women, before and at the end of a 12 day fast, and in eight normal controls under basal conditions. Hormonal 24 h IC and nyctohemeral variations were calculated from these data. Nyctohemeral rhythms were investigated by the periodogram method.

Patterns of plasma levels of prednisolone after oral administration in man

A competitive protein-binding method was found suitable for the estimation of plasma prednisolone levels in men in whom endogenous steroids were suppressed by dexamethasone premedication. This method is rapid and precise and allows measurements of prednisolone in small blood samples after usual therapeutic doses of the drug. Using this technique, two preparations of the medication were compared, a conventional form and an enteric-coated formulation; except for the delay due to the coating, they were completely comparable, since maximum levels reached, areas under the plasma concentration-time curves, and apparent disappearance half-lifes were almost identical.

PROLACTIN RELEASE AFTER INJECTION OF THYROTROPHIN-RELEASING HORMONE IN MAN

Abstract Five normal men were injected intra Summary venously 200 μg. of synthetic thyrotrophin-releasing hormone (T.R.H.). Blood was collected every 5 or 10 minutes and assayed for thyroid-stimulating hormone (T.S.H.), human growth hormone, luteinising hormone, hydrocortisone, and pituitary prolactin. T.S.H. levels reached peak values 20 to 40 minutes after the injection. Hydrocortisone, H.G.H., and L.H. did not exhibit any systematic variation. The T.R.H. injection was followed within 5 minutes by a release of prolactin, with a peak value at 10 minutes. These data indicate a lack of specificity of T.R.H. and suggest that in man it acts as a prolactin-releasing factor. Intravenous T.R.H. administration should become a very useful clinical test for the investigation of the hypothalamo-pituitary relationships, with special respect to prolactin secretion.

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

Abstract. 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 thyrotropir 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. Finall 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.

A combined radioimmunoassay for glucagon and insulin

SummaryA combined radioimmunoassay for glucagon and insulin in biological fluids is presented. It is based on the use of 131I-glucagon and 125I-insulin tracers and a charcoal-dextran separation procedure. Standard curves, sample determinations and recovery studies gave comparable results whether in the combined or individual assay for glucagon and insulin. The combined assay, especially if supported by a decoding and calculating computer program, offers the advantages that it requires a smaller volume of the material to be sampled, is more economical and less timeconsuming.

Specific inhibition by somatostatin of growth hormone release after hypoglycaemia in normal man

In normal man, synthetic linear somatostatin (growth hormone‐release inhibiting hormone) inhibits the growth hormone response to insulin induced hypoglycaemia, but has no influence on plasma levels of cortisol, prolactin, TSH and FSH.

Transport of cortisol, progesterone and cholesterol across isolated mesentery. Effect of metyrapone.

SummaryIsolated rat mesentery, mounted in a diffusion cell, is used as a model for the study of vascular endothelium permeability characteristics. The passage of tracer molecules is measured in the absence of osmotic or hydrostatic pressure gradients across the mesentery. The permeability coefficient of the membrane for cortisol and progesterone is similar. When bound to transcortin, cortisol crosses mesentery at a significantly slower rate. Metyrapone diatartrate increases by 30% the passage of free and of transcortinbound cortisol, but is without effect on the passage of progesterone or glucose in the same conditions. When the transfer of cholesterol across mesentery is studied, a high percentage of the tracer is trapped by the membrane.

Effects of dexamethasone and secobarbital on the pituitary response to thyrotropin releasing hormone (TRH) in man: synergistic inhibition of thyrotropin (TSH) release

The present study was made to investigate the possible effects of dexamethasone and secobarbital on the pituitary responses of prolactin (PRL) and TSH to TRH. Dexamethasone (1 mg) and secobarbital (10