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Biomedical subjects

T E Hilditch

Publications and source records attributed to T E Hilditch.

At least 55 records · Page 3Linked to original sources
PubMed1987

Radioprotective action of carbimazole in radioiodine therapy for thyrotoxicosis--influence of the drug on iodine kinetics.

Pretreatment with carbimazole of patients given radioiodine (131I) therapy for thyrotoxicosis reduces the incidence of early hypothyroidism. The possibility that this radioprotective effect might be a consequence of drug induced alteration in thyroidal iodide turnover, leading to a reduction in thyroid irradiation, was investigated in a prospective study of 24 thyrotoxic patients. Subjects were randomly assigned to receive 131I alone or to be treated with carbimazole for a minimum of three months before 131I. Thyroxine supplements were given in the latter group to prevent iatrogenic hypothyroidism. The effective half-life of therapeutic 131I in the thyroid was measured using a gamma camera/computer system after oral administration of the dose, allowing the biological half life of the anion and estimated radiation dose to the thyroid to be derived. Effective half life of 131I, biological half life of 131I and estimated radiation dose to the thyroid were similar in the two groups of subjects. It is concluded that the radioprotective action of carbimazole is not a consequence of altered thyroidal iodide kinetics.

Carbimazole↗
PubMed1987

False localization of an aldosteronoma by dexamethasone-suppressed adrenal scintigraphy.

A patient with primary aldosteronism had bilateral adrenal tumours on computed tomography. Selenocholesterol scintigraphy showed uptake by the larger right adrenal gland and a tumour in the gland was also visualized by venography. In contrast, measurements of aldosterone concentrations in adrenal venous blood lateralized to the left side. At surgery the left adrenal gland contained an aldosteronoma and the right adrenal gland a large non-functioning adenoma. Thus, selenocholesterol scintigraphy incorrectly localized the functioning adrenal tumour.

Adenoma↗
PubMed1987

Duration of antithyroid action of methimazole estimated with an intravenous perchlorate discharge test.

We have used a method based on a perchlorate discharge test to estimate the duration of antithyroid effect of two doses of methimazole (MMI). Six patients with diffuse toxic goitre took 5 mg MMI twice daily and six took 20 mg twice daily over the study period of 12 weeks. Biochemical control of hyperthyroidism was achieved in all patients and thyroid hormone supplementation was required by all of the patients in the higher dose group to avoid hypothyroidism. Discharge of radioiodine from the thyroid by perchlorate diminished in both groups with time after MMI. After 5 mg MMI, perchlorate discharge as a percentage of the 30-min uptake (mean +/- SD), was 81.7 +/- 3.3% at 2.2 h, 69.3 +/- 18.9% at 5.9 h, 22.6-23.4% at 13.4 h and 2.7-6.7% at 25.1 h. After 20 mg MMI, the discharge was 92.5 +/- 1.9% at 2.2 h, 84.3 +/- 8.8% at 6.3 h, 64.8 +/- 24.1% at 13.3 h and 26.9-29.4% at 25.1 h. Only four patients (one in the lower dose group) showed a detectable discharge at 25 h and one of the patients treated with the lower dose showed no discharge at 13 h. These estimates of the effect of MMI on thyroidal iodide organification are not in keeping with published thyroidal MMI concentrations which do not show a fall between 3-6 h and 17-20 h after carbimazole. The explanation for this disparity is not clear but may be based on a redistribution of thioureylenes within the thyroid with time after dosage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Formation of labelled colloid in 99Tcm-DMSA due to the presence of bactericidal fluid.

The possibility that traces of bactericidal fluid in 99Tcm-DMSA could lead to the formation of labelled colloid, was explored. In vitro investigations were undertaken using ultracentrifugation techniques and photon correlation spectroscopy. The latter showed that both contaminated and uncontaminated DMSA contained colloidal (or particulate) material. However the presence of 10 microliters bactericidal fluid as contaminant was shown by ultracentrifugation to result in labelling of this colloidal material when 99Tcm was added to DMSA. Studies in a normal volunteer confirmed the results of the in vitro studies, in that significant liver and spleen uptake was observed after the administration of contaminated 99Tcm-DMSA.

Anti-Infective Agents, Local↗
PubMed1986

Formation of large particles in a 99Tcm-tin colloid preparation.

The effect of prolonged continuous movement on particle size within a 99Tcm-tin colloid preparation was investigated, making use of photon correlation spectroscopy for size estimation. No increase in particle size was found when the preparation was left undisturbed for up to 7 h, the mean (+/- S.D.) size being found to be 239 +/- 24 nm. When the preparation was placed in a laboratory rotator for the same period of time, there was a gradual increase in mean particle size to 404 +/- 127 nm. The increase in size was much greater, however, after 7 h of continuous agitation in a laboratory shaker, a mean value of 2260 +/- 746 nm being observed. An antimony sulphide colloid was subjected to continuous agitation for the same period of time but there was no evidence of aggregation. It is supposed that continuous movement of reconstituted 99Tcm-tin colloid, leading to a marked increase in particle size, may explain occasional instances of significant lung intake.

Humans↗
PubMed1985

Quantitative 123I-iodide scintigraphy and radiation dosimetry in infants with congenital hypothyroidism.

Quantitative studies of 123I-iodide uptake using a gamma camera were undertaken in 23 infants with congenital hypothyroidism. Background oral radioactivity was reduced by ensuring that the infants drank fruit juice during the study. In 7 cases, there was no evidence of functioning thyroid tissue, in 13 cases, lingual tissue was present, and in 3 cases, there was uptake at the normal thyroid site. Dyshormonogenesis, as shown by a positive perchlorate discharge at 30-60 min after radioiodine administration, was present in 5 of the cases with demonstrable uptake. The estimated 20-min uptake of 123I-iodide was less than 2.6% of the dose in all cases except 1; in this case, the uptake was 10.4%, but this was completely discharged by perchlorate. There was good agreement between the quantitative radioiodine-uptake and -discharge results and the circulating thyroid-hormone levels. The estimated radiation dose to thyroid tissue using the technique was 9.2 mSv for an intravenous administration of 2MBq 123I-iodide.

Congenital Hypothyroidism↗
PubMed1985

Use of perchlorate to block gastric uptake of free 99Tcm in the investigation of gastrointestinal bleeding.

The use of perchlorate to block gastric uptake of free 99Tcm-pertechnetate after in vivo labelling of red cells was investigated. In 19 out of 20 cases there was no evidence that previous administration of perchlorate adversely affected red cell labelling using commercial stannous agents. Adequate scintigraphic images of the vascular system could be obtained for up to 24 h after the cells were labelled. The technique was found to be of value in the investigation of sites of gastrointestinal bleeding.

Colon↗
PubMed1985

Kinetics of [123I]iodide uptake and discharge by perchlorate in studies of inhibition of iodide binding by antithyroid drugs.

Thyroidal binding of iodide was studied by kinetic analysis of [123I]iodide uptake and its discharge by perchlorate in 80 hyperthyroid subjects receiving antithyroid drug therapy. Five dosage regimens ranging from 5 mg carbimazole twice daily to 15 mg methimazole twice daily were studied. Binding inhibition was estimated at 5-7 h after drug as an index of the mean effect of the 12 hourly regimen. In all cases, except one in the lowest dose group, binding was found to be markedly reduced with mean binding rates ranging from 0.002 to 0.020 min-1 (normal greater than 0.15 min-1). The net clearance of iodide in the lowest dose group was reduced to a mean value near the upper limit of the euthyroid range, whereas in the highest dose group it lay at the lower limit of the euthyroid range. These results were reflected in the serum thyroid hormone response. There was a reducing incidence of inadequate control of hyperthyroidism and an increasing incidence of hypothyroidism with increasing thiourylene dose. The exit rate constant of free iodide for the various doses showed values from 0.048 to 0.055 min-1. Corresponding mean values for the discharge rate constant after perchlorate were 0.087 to 0.105 min-1. This suggests that perchlorate increases the rate of iodide release from the thyroid gland. Studies at a later interval after drug (12-14 h) showed no change in discharge rate constant. This leads to the conclusion that perchlorate may further inhibit iodide binding in subjects receiving antithyroid drug therapy.

Antithyroid Agents↗
PubMed1984

Effect of pretreatment with carbimazole on early outcome following radio-iodine (131I) therapy.

Of a group of 55 thyrotoxic patients given therapeutic radio-iodine (131I), 24 were made euthyroid with carbimazole before 131I: the remainder were given 131I alone. Carbimazole was discontinued 5 days before 131I was administered. By 3 months after 131I treatment there was a greater incidence of hypothyroidism in the group given 131I alone (42% vs 25%), but a lower incidence of persistent thyrotoxicosis (16% vs 46%), (P less than 0.05). One year after treatment a similar proportion of each group had persistent thyrotoxicosis (21% vs 23%), but there remained a lower incidence of hypothyroidism in the group pretreated with carbimazole (25% vs 45%). It is suggested that pretreatment with carbimazole reduces the degree of radiation induced thyroid damage.

Aged↗
PubMed1983

Lacrimal scintigraphy. I. Compartmental analysis of data.

Linear compartmental analysis was applied to lacrimal scintigraphy data from asymptomatic and obstructed lacrimal systems. Failure to achieve satisfactory results in most of the asymptomatic systems studied suggests that variable tear flow is a feature of normal lacrimal drainage which precludes linear analysis. However, in cases where the analysis was successful the results were consistent with the occurrence of reflux between the conjunctival and lacrimal sacs, and between the lacrimal sac and nasolacrimal duct. Further support for the existence of reflux between compartments was provided by the analysis of obstructed systems, particularly those with obstruction at the upper end of the nasolacrimal duct. In such cases there was rapid equilibrium of the tracer between the conjunctival and lacrimal sacs, which in the absence of tear flow could be explained by reflux between these 2 compartments.

Computers↗
PubMed1983

Lacrimal scintigraphy. II. Its role in the diagnosis of epiphora.

Lacrimal scintigraphy (LS) was performed in 860 lacrimal drainage systems (LDS) in 188 patients with bilateral epiphora and 226 patients with unilateral epiphora. A very high incidence of canalicular obstruction was found in these patients, the incidence being higher in the group with unilateral epiphora. It is suggested that a canalicular block is a commoner cause of obstructive epiphora than has been recognised previously and that LS is a reliable method of studying the canalicular function. A significant number (42%) of the opposite asymptomatic eyes of patients with unilateral epiphora were found to have an abnormality in the LDS, which supports the view that abnormalities in the LDS tend to be bilateral. Only 25% of these asymptomatic systems showed a normal drainage, confirming that physiological obstruction can exist below the lacrimal sac in normal lacrimal drainage systems.

Adolescent↗
PubMed1983

Lacrimal scintigraphy. III. Physiological aspects of lacrimal drainage.

Lacrimal scintigraphy (LS) was performed on asymptomatic lacrimal drainage systems and the results were evaluated to understand the physiology of lacrimal drainage. It was found that a physiological obstruction can exist at the level of the nasolacrimal duct in normal asymptomatic individuals, and it is suggested that this obstruction is due to the resistance offered by the valve of Hasner, which in turn is dependent on (a) the volume of fluid in the lacrimal sac and the nasolacrimal duct, and (b) the anatomical integrity of the valve. The LS observations are taken into account to postulate a mechanism of drainage from the lacrimal sac into the nose, which hitherto has not been very clear. It is also suggested that reflux can occur between the various compartments of the lacrimal drainage system and that the various valves in the membranous passageway can become incompetent in an obstructed system.

Humans↗
PubMed1983

Transient hypothyroidism following radioiodine therapy for thyrotoxicosis.

A prospective study of thyroid function including serial tracer radioisotope uptake measurements in 55 patients treated with 131I therapy is described. Five patients had an episode of transient hypothyroidism within eight months of treatment: in three of these patients this was due to impaired organification of iodide, with normal iodide trapping by the thyroid (as measured by a twenty minute 123I uptake) being preserved. In contrast, in all patients who developed permanent hypothyroidism, iodide trapping was markedly diminished and did not recover. It is suggested that hypothyroidism due to organification failure following 131I therapy is potentially short-lived; where hypothyroidism is associated with gross impairment of iodide trapping, recovery is unlikely. Early iodine uptake measurements may be of value in selecting those patients whose hypothyroidism is transient and who do not require permanent thyroid hormone replacement.

Female↗