Chloride interference with use of an iodide-selective electrode for urinary I.
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Chlorides↗
Biomedical subjects
M S Croxson
Publications and source records attributed to M S Croxson.
Addison's disease, adrenal autoantibodies and computerised adrenal tomography.
The present study describes 53 patients with Addison's disease, who attended Auckland hospitals between 1971-1980, 32 of whom presented for the first time during this period, when the mean annual incidence of Addison's disease was 4.5 cases/million population, and the respective frequency of idiopathic (auto-immune) and tuberculous aetiologies was 92 percent and 4 percent for caucasians, but 25 percent and 63 percent for Polynesians. In addition, adrenal reserve was tested by ACTH stimulation in 20 clinically non-Addisonian patients in whom circulating adrenal antibodies had been incidentally demonstrated and present for periods of up to six years, and was normal in all cases. Such antibodies therefore lack functional disease specificity. The diagnostic value of CT adrenal scanning in illustrating the contrasting appearances between tuberculous and auto-immune adrenalitis is shown in four patients.
Addison Disease↗
Urinary immunoprecipitation method for estimation of thyroxine to triiodothyronine conversion in altered thyroid states.
A new method is described for the estimation of T4 to T3 conversion in man and is applied to the study of hyperthyroid and hypothyroid clinical states. The method employs simultaneous iv injection of [125I]T4 and [131I]T3 with isolation of the labeled T3 tracers in 4- to 8-day pooled urine samples by a combination of solvent extraction, desalting, and immunoprecipitation procedures. Using [131I]T3 as a recovery standard, the T4 to T3 conversion ratio was found to be 0.470 +/- 0.011 in euthyroid subjects. This confirmed our earlier findings of 0.482 +/- 0.014 using a paper chromatographic method and nonsimultaneous isotope administration. The conversion ratio was increased in hypothyroidism to 0.535 +/- 0.011 (P less than 0.02) and decreased in hyperthyroidism to 0.415 +/- 0.009 (P less than 0.01). These changes parallel the fraction of the radioiodine collected in the urine for both T4 and T3; normal values are 77 +/- 4% for T4 and 76 +/- 4% for T3, values in hypothyroidism are 79 +/- 1% for T4 and 79 +/- 3% for T3, and values in hyperthyroidism are 58 +/- 3% for T4 and 58 +/- 5% for T3 (P less than 0.01). These findings indicate that 1) urinary T4 to T3 conversion values are highly reproducible in euthyroid as well as hyperthyroid and hypothyroid states; 2) the reduction in T4 to T3 conversion in hyperthyroidism probably reflects increased T4 disposal by nondeiodinative pathways and possibly the reverse in hypothyroid states; and 3) since urinary T4 to T3 conversion values in euthyroid subjects exceeded all reported conversion values in blood, there may be an alternate pathway of T3 production and disposal which is not reflected in the blood T3 production rate.
Adult↗
TRH testing, T4-thyrotoxicosis and the aging thyroid gland.
Secondary thyroid function tests were compared in 41 mildly thyrotoxic and 36 euthyroid patients with an elevated free thyroxine index (FT4I). A serum TSH measurement 20 minutes after intravenous TRH (delta TSH) most reliably separates these two groups. A significant delta TSH response (greater than 0.5 microU/ml) is also helpful in excluding clinical thyrotoxicosis in patients with nodular goitre. The free T3 index was normal in one-third of mildly thyrotoxic patients and in all euthyroid patients with a falsely elevated FT4I. Blunted delta TSH responses to TRH in elderly New Zealand women were associated with nodular goitre or occult thyroid nodularity revealed only by thyroid scan. The reduced TRH responses are more likely due to partial thyroid autonomy than reduced synthetic capacity of thyrotrophs in old age.
Adolescent↗
A clinico-pathological study of 100 patients with solitary 'cold' thyroid nodules.
One hundred consecutive patients were studied at the Auckland Hospital thyroid clinic over a two year period 1974 to 1976, who subsequently had surgical excision of a solitary cold nodule. Thyroid carcinoma was present in 17 percent, adenoma in 44 percent, colloid nodules in 25 percent and a thyroid cyst in 14 percent. Although thyroid neoplasms were significantly more frequent in patients under 40, other clinical or scan features analysed were not predictive of carcinoma or neoplasm.
Adenoma↗
The effect of exercise, thyroid status and insulin-induced hypoglycaemia on the Achilles tendon reflex time in man.
The effect of moderate exercise on the Achilles tendon reflex half-relaxation time (ART) was observed in 28 hypothyroid, 35 euthyroid, and 20 hyperthyroid subjects of comparable age and sex. Both the resting ART and the decrease after exercise (delta ART) were longer in hypothyroid patients and shorter in hyperthyroid patients as compared to the euthyroid group. delta ART was strongly related to the resting ART rather than to the free thyroxine index. In four hypothyroid subjects, the half-time of recovery of the ART after exercise was similar, approx. 24 min. Insulin-hypoglycaemia in eight resting endocrine patients also caused a fall in ART similar to the post-exercise delta ART in the same patients. A possible catecholamine effect is indicated by the smaller post-exercise delta ART in nine hypertensive patients receiving chronic propranolol treatment, 320 mg daily, than that of a control group matched for age, sex, and resting ART. These studies suggest that submaximal exercise largely removes the differential effect of thyroid status on skeletal muscle contractility as measured indirectly by the ART. The effects of exercise and induced insulin-hypoglycaemia on delta ART may be mediated in part by endogenous catecholamines.
Achilles Tendon↗
A clinico-pathological study of two patients with Cushing's disease.
The clinical and autopsy findings are described in two patients with Crushing's disease who died five days and 18 years following bilateral adrenalectomy. In each case tomography of the pituitary fossa was normal but examination of the pituitary revealed a 5 to 6 mm basophilic adenoma in the antero-inferior aspect of the gland. The first patient failed to show suppression of urinary oxogenic steroids during administration of high dose dexamethasone. The second patient had functioning adrenal autografts in skeletal muscle 18 years after adrenalectomy. The clinico-pathological correlation of these two patients supports modern re-emphasis on the aetiology of Cushing's disease as a primary pituitary tumour and its treatment by selective trans-sphenoidal hypophysectomy.
Adenoma↗
Subclinical hypothyroidism.
Clinical and biochemical indices of thyroid function were compared in 18 euthyroid control subjects and 54 patients at risk of developing hypothyroidism, and the assessment repeated after a four-week trial of oral triiodothyronine (T3) 40 microgram daily. Patients with minor elevation of the pre-treatment serum TSH concentration (5-15 microU/ml) showed significant reduction in the free thyroxine index (FTI), prolongation of the basal ankle reflex half-relasation time (ART), and shortening of the ART after oral T3 treatment, when compared either to control subjects or to patients with a normal TSH level. It is concluded that patients with minimal TSH elevation have minor but parallel abnormalities of both thyroid hormone concentration and action.
Humans↗
Thyrotrophin displacement activity of serum immunoglobulins in health and disease.
A radioreceptor assay for TSH displacement activity (TDA) was employed as an index of thyroid stimulating immunoglobulins (TSlg) in serum from patients with autoimmune thyroid disease. TDA was less than or equal to 20 in normal subjects (37/37), patients without thyroid disease (36/38), non-toxic goitre (18/19) and toxic nodular goitre (16/17) and was significantly lower in Nepalese subjects with severe endemic goitre. TDA was greater than 20 in 84% of patients with untreated hyperthyroid Graves' disease (70/83), in Hashimoto's thyroiditis (3/17) and following subtotal thyroidectomy (8/14) or 131I therapy (7/11), but was less than or equal to 20 in euthyroid patients treated with carbimazole (58/59) and during spontaneous remission (18/19). Serial TDA measurements during antithyroid drug therapy suggested that carbimazole has a direct effect in reducing TSlg concentration but that TDA is not a useful prognostic indicator of short term relapse or remission.
Autoimmune Diseases↗
Triiodothyronine-secreting (toxic) adenoma of the thyroid gland: light and electron microscopic characteristics.
A patient with thyrotoxicosis due to a triiodothyronine (T3)-secreting autonomous adenoma is described. The histmorphology of the neoplasms was similar to other neoplasms previously reported. Ultrastructural features of the adenoma are compatible with a very actively secreting follicular cell and are best compared with the ultrastructure of a diffuse toxic goiter. Distinctive features that separate toxic adenomas from various thyroid carcinomas and normal thyroid parenchyma are discussed.
Adenoma↗
Effects of thyroid hormone on plasma adenosine 3',5'-monophosphate production in man.
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Cyclic AMP↗
Low serum triiodothyronine (T3) and hypothyroidism in anorexia nervosa.
Measurements of serum thyroid hormones were compared in 22 patients with typical anorexia nervosa and 22 euthyroid control subjects. Serum total triiodothyronine (T3) was (mean +/- (SE) 62.1 +/- 7.1 ng/100 ml in anorexia patients and 115.2 +/- 8.4 ng/100 ml in control subjects (P less than 0.001). Serum adjusted thyroxine (T4Adj) was significantly different in the anorexia (7.1 +/- 0.4) and control (8.2 +/- 0.4) groups. Serum T3 was subnormal in 63% and T4Adj subnormal in 36% of the 22 anorexia patients. The mean serum T4/T3 in anorexia patients (158 +/- 19) was higher than that in the control subjects (88 +/- 5.5, P less than 0.005) or in 18 patients with hypothalamic or pituitary hypothyroidism (77.9 +/- 10.1, P less than 0.001). Following weight gain in 6 anorexia patients, there was a significant rise in serum T3 without change in T4Adj concentration. The Achilles reflex half-relaxation time (ART) in 38 anorexia patients was 348.6 +/- 10 msec compared with 280 +/- 30 msec in 168 normal age-matched subjects (P less than 0.001), and was prolonged (greater than 340 msec) in 65% of these 38 patients. In 18 anorexia patients with measured ART, T3 and T4Adj, the mean ART was longer 376.1 +/- 20 msec) in 10 with subnormal T3 than in 8 patients with a normal T3 (294.7 +/- 13.2 msec, P less than 0.01). There was no significant difference in the mean ART between patients with a normal or low serum T4Adj. Administeration of oral T3 40 mug/day for 4 weeks to 11 anorexia patients caused a significant reduction (P less than 0.001) in mean ART of 108.7 +/- 9.6 msec compared with 17.7 +/- 3.3 msec in 18 normal subjects. There was a normal peak serum TSH and a rise in mean total serum T3 of 47 +/- 12 ng/100 ml (range 11-100 ng/ml) in 7 of 8 patients following 200 mug of iv thyrotropin releasing hormone (TRH). The fall in serum TSH was delayed in 6 patients. Assessment of hypothalamic control of thyroid function in 3 patients using the method of thyroidal iodide release (TIR) showed impairment of the normal diurnal variation and response to administered glucocorticoids. In the absence of a space-occupying pituitary lesion, the TRH and TIR data suggest a central inhibition of thyroid function, possibly by impairment of hypothalamic TRH release. In addition, a probable decrease of peripheral T4 to T3 conversion leads to low serum T3 concentrations. The prolonged basal ART and the marked ART reduction in response to T3 administration is attributed to correction of tissue thyroid hormone deficiency in the anorexia patients.
Achilles Tendon↗
Lack of indomethacin effect on thyroid function in man.
Administration of indomethacin 200 mg daily for 2 days to four euthyroid volunteers was without significant effect on serum triiodothyronine or thyroxine and caused no cinsistent alteration of serum TSH. There were minor and variable changes in the pattern of thyroidal iodine release (TIR) in these euthyroid subjects. In one subject both the TIR pattern and serum TSH concentration were altered in the same direction, suggesting that these minor changes were of central origin. Indomethacin also had no effect on the stimulated pattern of TIR in one euthyroid subject receiving daily exogenous TSH injections, or in a patient with untreated hyperthyroid Graves' disease. Prostaglandin A1 infusion in one subject did not alter serum TSH or thyroidal iodine release. It is concluded that prostaglandins probably have no obligatory physiological role in modulating TSH or thyroid hormone secretion in man.
Adult↗
Decreased serum thyrotropin induced by fasting.
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17-Hydroxycorticosteroids↗
Failure of triiodothyronine to inhibit TSH-mediated thyroid hormone release in man.
We studied the effect of short-term triiodothyronine administration on thyroid gland responsivity to exogenous thyrotropin in four euthyroid human subjects. Thyroidal iodine release and serum thyroxine during daily im injections of bovine TSH were not significantly inhibited, despite a four-fold elevation in serum T3 concentrations. This negative finding contrasts with earlier positive reports of a regulatory "short-loop" effect of elevated circulating T3 on the thyroid gland. This difference may be due either to the use in previous murine or in vitro studies of non-physiologic, high doses of exogenous T3, or failure to control the withdrawal of the trophic effect of endogenous TSH in man on the subsequent glandular response.
Adult↗
Combination drug therapy for treatment of hyperthyroid Grave's disease.
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Adult↗
The acute thyroidal response to iodixed oil in severe endemic goiter.
The acute changes in serum thyrotropin (TSH) triiodothyronine (T3) and thyroxine (T4), were measured in 14 subjects, 4 to 10 (mean = 6) days following intramuscular iodized oil injection. In 8 subjects with small or absent goiter there was a significant fall in T3 and a rise in TSH concentrations, suggesting an acute inhibitory effect of the iodine. In 6 subjects with large multinodular goiters there was a marked rise in both T3 and T4, and reduction in the elevated basal TSH. Biochemical hyperthyroidism occurred in 3 of these subjects. The acute thyroid hormone response to iodized oil, whether inhibitory or stimulatory in a particular subject, depends both on goiter size and on the serum concentration of TSH.
Adolescent↗
Serum digoxin in patients with thyroid disease.
Serum digoxin concentrations were measured by radioimmunoassay in 17 hyperthyroid and 16 hypothyroid patients after a seven-day course of oral digoxin. The significantly higher levels of serum digoxin in patients with hypothyroidism and lower levels in those with hyperthyroidism were closely related to the measured changes of glomerular filtration rate and digoxin serum half time in these two groups. Differences in serum digoxin concentration contribute to the altered sensitivity to digoxin shown by patients with thyroid disease.
Administration, Oral↗