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Biomedical subjects

R D Utiger

Publications and source records attributed to R D Utiger.

At least 145 records · Page 8Linked to original sources
PubMed1969

The effect of glucocorticoids on thyrotropin secretion.

The effect of large doses of glucocorticoids on thyrotropin (TSH) secretion in normal and hypothyroid humans has been studied. Plasma TSH concentrations were measured before, during, and after treatment with dexamethasone given orally for 24-48 hr. In 17 patients with primary hypothyroidism, plasma TSH levels fell significantly during treatment to a mean of 54% of control (range 23-96%). Within 48 hr after the withdrawal of dexamethasone, TSH concentrations transiently increased above pretreatment values. The mean increase was to 156% of control (range 106-294). Similar changes, but of smaller magnitude, were observed in 15 normal subjects. Administration of single oral doses of dexamethasone and oral or intravenous doses of cortisol were followed by reduction of plasma TSH levels to 18-47% of control within 8-12 hr in eight hypothyroid patients. This fall also was followed by significant TSH rises above control values before they returned to the pretreatment levels. Mineralocorticoid administration was not followed by any changes in plasma TSH concentrations in three subjects.TSH responses to steroid were also studied in rats. In hypothyroid rats given dexamethasone intravenously, plasma TSH fell to 63% of control in 30-90 min and then returned to normal or above in 3-4 hr. Dexamethasone also reduced plasma TSH concentrations in normal rats but no rebound was observed in these animals. Dexamethasone did not block the increase in plasma TSH produced by thyrotropin releasing factor (TRF) administration in vivo. Neither basal nor TRF-mediated TSH release from hemipituitaries in vitro was reduced by dexamethasone or corticosterone. These studies indicate that glucocorticoids reduce TSH secretion and suggest that this effect occurs at a suprahypophyseal level.

Animals↗
PubMed1967

Estimation of the secretion rate of thyrotropin in man.

The plasma concentration of a pituitary hormone is determined by the rate of secretion, degradation, and the volume of distribution of that hormone. Using a radioimmunoassay for human thyrotropin (TSH) and human TSH-(131)I, we have estimated the rates of degradation and distribution of TSH in man and calculated the rate of secretion. Either 0.5 or 5 mug of TSH-(131)I with specific activities of 1 to 50 muc per mug was administered intravenously to 12 euthyroid subjects. Serial determinations were made of TSH-(131)I, and the half-time of disappearance (t((1/2))) was thus estimated. The average t((1/2)) in euthyroid subjects was 53.9 minutes with a volume of distribution averaging 5.8% of body weight. The mean endogenous plasma TSH concentration was 1.8 mmug per ml (2.7 muU per ml in terms of the human TSH reference standard A). The mean total TSH pool, excluding the pituitary, was 5.8 mug (8.7 mU). From these data the mean secretion rate of TSH in euthyroid man was calculated to be 110.1 mug per day (165.2 mU). Similar data were estimated for 3 mildly hypothyroid patients. The t((1/2)) were 75.1, 97.1, and 83.6 minutes, with a mean of 85.3 minutes (1.6 times normal). The mean TSH pool was 58.1 mug (10 times normal). The secretion rate was 688.7 mug per day (1,033.1 mU). In other hypothyroid patients, plasma TSH levels ranging from 6 to 230 mmug per ml (9 to 345 muU) have been found. If similar half-times and a normal distribution volume are assumed, the secretion rate of TSH in hypothyroid patients can be estimated to range from about 260 to 15,350 mug per day (390 to 23,025 mU) or from about 2 to 307 times normal. Therefore, the elevated plasma TSH levels found in hypothyroidism are a result of both slower degradation and increase in rate of secretion.

Adolescent↗