Biomedical subjects

J Weeke

Publications and source records attributed to J Weeke.

At least 91 records · Page 5Linked to original sources

PubMed1978

Circadian and 30 minutes variations in serum TSH and thyroid hormones in normal subjects.

Ten normal young males were investigated in order to examine diurnal and short-term variations in serum TSH and serum thyroid hormones. In five subjects blood samples were obtained every 30 min during a 24 h period of daily life. A synchronous diurnal rhythm was found for free T3 and serum TSH with low levels in the day-time and higher levels at night. The mean increase from day to night was 15 and 140 per cent, respectively. There was a tendency to a similar rhythm in free T4, but the increase of 7 per cent fell short of statistical significance. In the other five men blood samples were obtained every 5 min in a 6 to 7 h period starting within the interval from 19.15 to 22.00 h. A significant regular variation with a cycle-length of half an hour was found in TSH, free T3 and free T4. This rhythm accounted for a significant part of the total variation in the levels of TSH, free T3 and free T4. The mean amplitude of the short-term variation is 13, 15 and 11 per cent of the mean level of the respective hormones. The data suggest a pulsatile release of hormones from the thyroid gland governed by a pulsatile TSH secretion.

Adult↗

PubMed1978

24-hour studies of the effects of somatostatin on the levels of plasma growth hormone, glucagon, and glucose in normal subjects and juvenile diabetics.

Somatostatin was infused in various doses into normal subjects and juvenile diabetics for a 24-hour period preceded by a 24-hour control period and followed by another three-hour control period. Saline was infused during the first control period. Meals were served during the two 24-hour periods. Blood samples were taken hourly. Five normal males received a total dose of 4 mg. somatostatin. Four male diabetics received 2 mg., four received 4 mg., and four 6 mg. In the diabetics, somatostatin suppressed plasma growth hormone, glucagon, and glucose throughout the infusion. All parameters rebounded at cessation of infusion. In the normals, somatostatin suppressed plasma growth hormone, glucagon, and insulin but increased plasma glucose. It is concluded that the plasma glucose suppression in the diabetics is mainly due to the suppression of the diabetogenic hormones growth hormone and glucagon. A minor effect of decreased and/or delayed absorption of carbohydrates cannot be excluded in these experiments. The elevated plasma glucose levels in normals must be due to the suppressive effects of somatostatin on insulin secretion.

Adolescent↗

PubMed1977

Propranolol-induced increments in total and free serum thyroxine in patients with essential hypertension.

The effect of propranolol on serum levels of total and free thyroxine, total and free triiodothyronine, and thyroid-stimulating hormone (TSH) was investigated in 15 clinical euthyroid patients with essential hypertension. Oral propranolol in dosages from 80 to 480 mg/day for a 30-day period induced an average increase in total serum thyroxine of 15.5 +/- 2.2% (mean +/- SEM, 2 p = 0.00002) and in free thyroxine of 17.7 +/- 3.5% (2 p = 0.00009). The oral dose of propranolol correlated positively with serum propranolol (r = 0.70, 2 p = 0.007). No significant correlation between serum propranolol and changes in serum thyroxine could be demonstrated. Total and free triiodothyronine, as well as TSH, remained unchanged during propranolol treatment. The most likely explanation is a propranolol-induced decreased degradation of thyroxine. A practical consequence is that in patients with an uncertain clinical picture and slightly elevated serum thyroxine, propranolol intake should be considered.

Adolescent↗

PubMed1977

Radioimmunological determination of reverse triiodothyronine in unextracted serum and serum dialysates.

A sensitive radioimmunoassay for measurements of 3,3'-5'-triiodothyronine (reverse T3, rT3) in small amounts of unextracted serum is described. The interference of rT3 binding proteins in serum was precluded by addition of 8-anilino-1-naphthalene sulphonic acid (ANS). The cross reaction of T4 with the rT3 anti-serum varied with the concentration of T4 in the samples. At 50 per cent inhibition of [125I]rT3 binding, the T4 cross reaction was 0.075% (mol/mol). All values were corrected for T4 cross reaction. By the present method total rT3 averaged 0.37 nmol/l in thirty-two normal subjects. Higher values (0.81-1.98 nmol/l) were obtained in seventeen thyrotoxic patients, while the rT3 was very low (less than or equal to 0.046 nmol/l) in ten patients with severe primary hypothyroidism. A modification of the total rT3 assay was used for measurements of rT3 in serum dialysates (free rT3). The sensitivity was 0.46 pmol/l. This sensitivity did not allow detection of free rT3 in all normal subjects.

Adult↗

PubMed1976

Diural TSH variations in hypothyroidism.

There is a circadian variation in serum TSH in euthyroid subjects. A similar diurnal variation has been demonstrated in patients with hypothyroidism. In the present study the 24-hour pattern of serum TSH was investigated in eight patients with hypothyroidism of varying severity and in five hypothyroid patients treated with thyroxine (T4). There was a circadian variation in serum TSH in patients with hypothyroidism of moderate degree, and in patients treated for severe hypothyrodism with thyroxine. The pattern was similar to that found in normal subjects, i.e., low TSH levels in the daytime and higher levels at night. In severely hypothyroid patients, no diurnal variation in serum TSH was observed. A practical consequence is that blood samples for TSH measurements in patients with moderately elevated TSH levels are best taken after 1100 h, when the low day levels are reached.

Adult↗

PubMed1975

The response of thyrotropin and triiodothyronine to various doses of thyrotropin releasing hormone in normal man.

The relationship between serum thyrotropin (TSH) and serum triiodothyronine (T3) before and after injection of different doses of thyrotropin releasing hormone (TRH), given as single injections or as multiple injections with short intervals, was investigated in normal men. A positive correlation between prestimulated serum TSH and serum T3 levels and between the increase in the serum TSH and the serum T3 levels after TRH was found when repeated tests were performed in the same individual. There was a dose dependent TSH and T3 response to TRH. The smallest dose that produced a maximal response of both TSH and T3 was only 30 mug TRH. After six injections of 30 mug TRH with an interval of 30 minutes the increase in TSH was two times and the increase in T3 was three times as high as the maximal increase after single injections of TRH. This test with multiple injections of TRH may prove to be of clinical value in the measurement of both pituitary and thyroid function in selected patients. The close positive correlation between the serum TSH and serum T3 levels in basal conditions, demonstrated in four normal subjects in this study, probably reflects the steady state level determined by the hypothalamus from which the feedback control of TSH secretion operates.

Adult↗

PubMed1975

Inhibition by somatostatin of basal levels of serum thyrotropin (TSH) in normal men.

To elucidate the effect of somatostatin on basal, unstimulated TSH secretion 6 young healthy nonobese men were studied with blood samples every 15 min from 2300 h to 0500 h. Somatostatin 1 mg was indused over a 2-h period from 0100 h. One of the subjects was also studied with half hourly blood samples throughout a 26-h period without receiving somatostatin. In all cases the high night levels of serum thyrotropin (TSH) were significantly suppressed by somatostatin. The fall of TSH continued throughout the two hour infusion period. Immediately upon termination of the infusion serum TSH increased rapidly to preinfusion values. The 26-h control study showed the typical diurnal pattern of serum TSH with low values in the daytime and high values at night. The serum triiodothyronine (T3) and thyroxine (T4) levels were not changed by somatostatin infusion. From these results we suggest that endogenous somatostatin may be of physiological importance in the regulation of the TSH secretion.

Adult↗

PubMed1975

Serum tsh and serum t3 levels during normal menstrual cycles and during cycles on oral contraceptives.

Serum TSH and serum T3 levels were studied in 35 normally menstruating women and in 35 women on oral contraceptives in order to find out whether the levels of TSH and T3 were related to the menstrual cycle or changed by oral contraceptives. Serum TSH AND T3 were found to be unchanged throughout the normal menstrual cycles and during the cycles of oral contraceptives. The TSH level was higher in the women on oral contraceptives than in the normally menstruating women. This might be due to a direct thyroid inhibitory effect of oestrogen. As could be expected the levels of T3 and T4 were higher in women on oral contraceptives than in normally menstruating women.

Contraceptives, Oral↗

PubMed1975

T3 release from thyroid slices as an assay for thyroid stimulators.

A new in vitro bioassay for thyroid stimulators is described. The method is based on radioimmunological measurement of triiodothyronine (T3) release from thyroid slices. Small thyroid slices were cut from several porcine thyroids. The slices were pooled in incubation vessels. The stimulating effect of human thyroid-stimulating hormone (TSH), bovine TSH, and serum from a patient with Grave's disease was investigated. After 3 hr the T3 concentration was significantly higher in the vessels containing the thyroid stimulators than in the control vessels. For maximal sensitivity 16 hr of incubation was used in the assay. Bovine TSH, human TSH, and serum from a patient with Grave's disease gave linear dose response curves in a log-log system. For bovine TSH the curve was linear from 5 to 125 muU/ml incubation medium. The dilution curves for bovine TSH and serum from a patient with Grave's disease were parallel. The dilution curve for human TSH was considerably steeper. In 5 assays the lambda values for the bovine TSH curves were 0.10-0.16 (mean, 0.12). In 3 assays the lambda values for the human TSH curves were 0.05-0.07.

Animals↗

PubMed1975

Ultrasensitive radioimmunoassay for direct determination of free triiodothyronine concentration in serum.

Free triiodothyronine (T3) in serum has been measured directly in dialysates of serum, using a wick chromatographic radioimmunoassay. Adequate sensitivity was attained by the use of [1251]T3 with very high specific activity (2,000 to 3,000 muCi/mug). Sera were dialysed against a Krebs-Ringer bicarbonate buffer modified so as to be similar to plasma water. Dialysis took place under carefully controlled circumstances. The influence on the equilibrium of total to free T3 of temperature, serum dilution, and dialysis time was studied. By the present method, free T3 in serum from groups of subjects including 20 men, 10 women taking oral contraceptives, and 20 women with normal menstrual cycles were identical, averaging 5.2 pg/ml. A chromatographic radioimmunoassay of total T3 using high specific activity [1251]T3 and very small test samples is also described.

Anilino Naphthalenesulfonates↗

PubMed1974