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Biomedical subjects

M R Hopton

Publications and source records attributed to M R Hopton.

11 recordsLinked to original sources
PubMed1993

Humoral hypercalcaemia in renal carcinoma due to parathyroid hormone related protein.

Parathyroid hormone related protein (PTHRP) has been implicated in humoral hypercalcaemia of malignancy (HHM). We describe a patient with a renal carcinoma and hypercalcaemia, and for the first time have demonstrated a 4-fold PTHRP concentration gradient across a renal tumour bed. This provides further strong evidence that the primary tumour was the source of the PTHRP. The PTHRP 1-86 content of the tumour tissue was 4.8 ng/g, similar to that previously found in tumours associated with HHM. In PTHRP-secreting tumours, PTHRP may be a useful oncological marker after surgical resection.

Biomarkers, Tumor↗
PubMed1986

Immunoradiometric assay of thyrotropin as a "first-line" thyroid-function test in the routine laboratory.

We compared the utility of a sensitive immunoradiometric assay for serum thyrotropin as a "first-line" thyroid-function test with a strategy based on first measuring total thyroxin in serum. The immunoradiometric assay appears to distinguish primary hypothyroidism and hyperthyroidism from euthyroidism in "new" patients. The role of this test in monitoring antithyroid treatment or thyroxin-replacement therapy is not yet established, there being particular difficulty in interpreting low thyrotropin concentrations in such patients. Nevertheless, because a normal thyrotropin concentration in most, if not all, situations signifies the euthyroid state, thyrotropin determination by immunoradiometric assay merits consideration as an initial test by laboratories performing thyroid-function tests.

Antithyroid Agents↗
PubMed1985

Circannual and within-individual variation of thyroid function tests in normal subjects.

Blood was taken from normal subjects at monthly intervals over a period of one year for subsequent determination of serum thyroid hormone concentrations. Thyroid-stimulating hormone (TSH) responses to TSH-releasing hormone were performed at 3-monthly intervals. This study provided data on within-individual variation and on seasonally-related changes of these thyroid function tests. The results showed that, within an individual, thyroid hormone concentrations are maintained within narrow limits. For both thyroxine and triiodothyronine the component contribution of within-individual variation to the population-based variation (the latter also termed the 'reference interval', or colloquially the 'normal range') was small. This high degree of individuality implies that rigorous comparison of thyroid hormone results against a population-based 'normal range' can be potentially misleading. Despite the limited within-individual variation, seasonally-related changes in thyroid hormone concentrations were apparent, with higher thyroxine and triiodothyronine values seen in winter months. A tendency to a greater TSH response to TSH-releasing hormone was also noted at this time. Conceivably these changes could reflect a centrally-mediated response of the hypothalamic-pituitary-thyroid axis to environmental temperature.

Biological Clocks↗
PubMed1984

The effects of ranitidine on pituitary-thyroid function.

Although several studies have examined the effects of cimetidine on pituitary-thyroid function, few have investigated ranitidine in this respect. We found no changes in thyroid-stimulating-hormone (TSH) or prolactin responses to TSH-releasing-hormone (TRH) in 10 patients with peptic ulcer disease given oral ranitidine. Serum total and free thyroxine (TT4 and FT4) concentrations declined slightly, whereas total and free triiodothyronine (TT3 and FT3) increased slightly following ranitidine. None of these changes achieved statistical significance. Both the ratio of TT4/TT3 and FT4/FT3, however, declined (P less than 0.05) following ranitidine. Thus ranitidine may have a minor influence on peripheral deiodination of thyroxine but has little effect on hormone production from the thyroid gland. The diagnostic value of biochemical tests of thyroid function is not seriously compromised in patients receiving ranitidine.

Adult↗
PubMed1984

Myoglobin concentration, creatine kinase activity, and creatine kinase B subunit concentrations in serum during thyroid disease.

Changes in values for myoglobin, total creatine kinase (EC 2.7.3.2), and creatine kinase B-subunit in the serum of patients with thyroid disease are compared with values for these during the 24-h after myocardial infarction. Concentrations of all three of these muscle-derived proteins were significantly higher than normal in patients with primary hypothyroidism, and declined with treatment. Values for total creatine kinase activity were below-normal in hyperthyroid patients, but increased after treatment. Values for total creatine kinase and, to a lesser extent, myoglobin in hypothyroidism extend into the range of values observed after myocardial infarction. The mechanism of the changes in these analytes in hypothyroidism may be related to increased leakage from skeletal-muscle cells or diminished clearance from the circulation, or both.

Creatine Kinase↗
PubMed1983

Serum free thyroxine concentration and free thyroid hormone indices in normal pregnancy.

Serum free thyroxine (FT4) concentrations were shown to be significantly reduced at 36-38 weeks normal pregnancy, both as measured FT4 by the Amerlex method (P less than 0.001), and as calculated FT4 (P less than 0.001) using accepted molecular weight and affinity constant data for the binding proteins. Serum FT4 concentrations as determined by the Immophase method were normal at 36-38 weeks normal pregnancy. All methods gave normal serum FT4 concentrations in subjects taking the oral contraceptive pill. FT4I and FT3I, derived using the MAA T3 uptake-value, were higher than normal at 36-38 weeks pregnancy (P less than 0.001), whereas T4/TBG and T3/TBG were both reduced (P less than 0.001). The observation that serum FT4 concentrations may fall in late pregnancy, as demonstrated both by the Amerlex radioimmunoassay technique and by calculation, suggests that circulating FT4 may not be the sole determinant of thyroid status at this time. From a practical viewpoint, it is important to note that currently available direct and indirect methods of assessing serum FT4 concentrations produce different patterns of change in pregnancy.

Adult↗
PubMed1983

Serum free thyroxine concentrations in subjects with high circulating levels of thyroxine-binding globulin.

Serum free thyroxine (FT4) and thyroid hormone-binding protein concentrations were measured in pregnant women, stilboestrol-treated patients, and subjects with congenital thyroxine-binding-globulin (TBG) excess. In pregnant and stilboestrol-treated patients matched for TBG concentrations, serum FT4 concentrations measured by the Amerlex technique and by calculation, were reduced, as also was the total thyroxine (TT4)/TBG ratio. In congenital TBG excess Amerlex and calculated FT4 concentrations were normal whereas the TT4/TBG ratio was low. In contrast to the Amerlex method, FT4 concentrations by the Immophase procedure were normal in pregnant and stilboestrol-treated individuals and high in congenital TBG excess. We conclude that (i) reduced FT4 concentrations in pregnancy are related to an oestrogen effect rather than to some other pregnancy-associated factor, (ii) the TT4/TBG ratio gives a misleading indication of FT4 concentration in congenital TBG excess, and (iii) that when TBG concentrations are raised Immophase gives higher FT4 values than Amerlex or calculation when each is compared to FT4 values in their normal respective control group.

Adult↗
PubMed1981

Concentration of serum thyroid hormone binding proteins after 131I treatment of hyperthyroidism.

Serum concentrations of the thyroid hormone binding proteins, thyroxine binding globulin, prealbumin, and albumin were determined in 30 thyrotoxic patients before and after 131I treatment. Each patient was placed into one of three groups according to response to treatment. The serum concentration of all three proteins rose significantly in 10 patients who became euthyroid, and a greater increase was seen in 10 patients who developed hypothyroidism. There was no significant change in thyroid hormone binding protein concentrations in 10 subjects who remained hyperthyroid. Changes in the concentration of thyroid hormone binding proteins should be borne in mind when total thyroid hormone concentrations are used to monitor the progress of patients receiving treatment for hyperthyroidism.

Humans↗