Acidic isoforms of chorionic gonadotrophin in European and Samoan women are associated with hyperemesis gravidarum and may be thyrotrophic.

OBJECTIVE: There is conflicting evidence concerning the role of human chorionic gonadotrophin (hCG) in the aetiology of hyperemesis gravidarum (HG); particular isoforms of hCG may be the critical factor. Ethnic differences in HG prevalence and putative thyrotrophic effects of hCG may also relate to differences in hCG isoform profiles. To address these issues we examined the relationship of hCG isoforms to HG and thyroid function tests in two groups of women from ethnic backgrounds with significantly different HG prevalence rates. PATIENTS AND DESIGN: We enrolled 10 European and 10 Samoan women with HG and an equally sized non-hyperemetic, gestational stage matched control group. MEASUREMENTS: We administered a questionnaire, generated serum hCG charge-isoform profiles by chromatofocusing and measured the serum concentrations of total hCG, oestradiol (E2), thyrotrophin (TSH) and free thyroxine (FT4). RESULTS: The mean serum total hCG levels were highest in the Samoan hyperemetics (176,268 IU/l), and overall higher in hyperemetics compared with controls (159,770 IU/l vs. 86,420 IU/l, P < 0.001). When compared with controls, hyperemetics displayed increased hCG concentrations in the more acidic half (pH < 4) of the chromatofocusing pH range (89,843 IU/l vs. 41,146 IU/l, P < 0.003). Serum E2 levels did not differ between the four groups, but correlated with the hCG concentration between pH 5.2 and 4.01. Mean serum TSH levels were significantly lower in hyperemetics than in controls (0.33 mIU/l vs. 1.19 mIU/l, P < 0.001) and correlated with the hCG concentration between pH 4.6 and 2.8, while serum FT4 correlated with the hCG concentration below pH 4.0. CONCLUSIONS: Acidic isoforms of hCG may play a role in the aetiology of HG and gestational thyrotoxicosis. Minor ethnic differences in hCG isoform profiles were observed, but the relationship of acidic hCG isoforms to HG and serum thyroid hormone levels was largely independent of the patients' ethnicity. The mechanisms by which acidic isoforms might provoke nausea remain uncertain, but do not seem to involve E2, while the longer half-life of acidic hCG isoforms may result in increased in vivo TSH receptor cross-talk with resultant thyrotrophic effects.

A randomized trial of short-term treatment of Graves' disease with high-dose carbimazole plus thyroxine versus low-dose carbimazole.

OBJECTIVE: The optimal treatment regimen with thionamide drugs remains a matter for debate. We have investigated whether high doses of carbimazole, when compared with low doses, reduce relapse rates of Graves' disease. DESIGN: In an open label, randomized, prospective trial of treatment of Graves' disease we compared high doses of carbimazole (6 months of 100 mg carbimazole per day plus thyroxine) to low-dose carbimazole treatment (starting at 25 mg and titrating the carbimazole dose with the aim to maintain serum thyroid function test results within the normal reference range). PATIENTS: Thirty-seven patients with a first episode of Graves' disease were enrolled. MEASUREMENTS: During the 6 months of treatment we evaluated the rate of normalization of serum thyroid function tests, changes in serum thyroid auto-antibody levels and the rate of side-effects during treatment. After completion of the 6-month treatment course patients were observed for 2 years for evidence of relapse of Graves' disease. RESULTS: There were no differences between the two groups either in the rate of normalization of serum thyroid function tests or in serum thyroid auto-antibody levels during treatment. Of the 17 patients randomized to high-dose treatment seven suffered treatment side-effects, compared to only one of the 20 patients receiving low-dose treatment (P < 0.006). There was no significant difference in 2-year post-treatment remission rates on an intention-to-treat basis between the two treatment groups (18.7% vs. 5.9%, P = NS). However, for those patients who completed 6 months of treatment (high-dose group = 9, low-dose group = 16), multivariate survival analysis demonstrated a significantly longer median relapse-free interval (P < 0.04) in the high-dose group (27 weeks; 25th percentile: 9.6 weeks, 75th percentile: 75 weeks) versus the low-dose group (6 weeks; 25th percentile: 4.8 weeks, 75th percentile: 13.1 weeks). CONCLUSIONS: High-dose carbimazole treatment delays, but does not prevent, relapse from Graves' disease in those patients able to tolerate the treatment. However, it leads to more frequent side-effects than conventional dose treatment.

Treatment of hypothyroidism with once weekly thyroxine.

We compared daily T4 therapy with 7 times the normal daily dose administered once weekly in 12 hypothyroid subjects in a randomized cross-over trial. At the end of each treatment we measured serum free T4 (FT4), free T3 (FT3), rT3, and TSH levels and multiple markers of thyroid hormone effects at the tissue level repeatedly for 24 h. Compared with daily administration, the mean serum TSH before the administration of weekly T4 was higher (weekly, 6.61; daily, 3.92 microIU/mL; P < 0.0001), and the mean FT4 (weekly, 0.98; daily, 1.35 ng/dL; P < 0.01) and FT3 (weekly, 208, daily, 242 pg/dL; P < 0.01) were lower. A minimally elevated serum total cholesterol during weekly administration (weekly, 246.8; daily, 232.6 mg/dL; P < 0.03) was the only evidence of hypothyroidism at the tissue level. Compared with daily administration, the mean peak FT4 following weekly administration of T4 was significantly higher (weekly, 2.71; daily, 1.59 ng/dL; P < 0.0001), as was the mean peak FT3 level (weekly, 285; daily, 246 pg/dL; P < 0.01). None of the tissue markers of thyroid hormone effect changed compared to daily T4, and there was no evidence of treatment toxicity, including cardiac toxicity. During weekly T4 administration, autoregulatory mechanisms maintain near-euthyroidism. For complete biochemical euthyroidism a slightly larger dose than 7 times the normal daily dose may be required.

Serum free thyroxine levels in cats maintained on diets relatively high or low in iodine.

Excessive or deficient intake of iodine may play a role in the development of goitre and hyperthyroidism in cats. Previous investigations have shown that the serum free thyroxine level of cats is affected by brief administration of food high or low in iodine content. We have now measured serum free thyroxine levels in groups of cats fed relatively high or low iodine diets for much longer periods (5 months). In contrast to our earlier findings, the chronic ingestion of relatively high or low iodine diets did not lead to statistically significant differences in serum free thyroxine levels. The results of the present investigations show that the cat is able to maintain normal levels of thyroid hormone despite prolonged high or low iodine diets. It may be that the adaptive mechanisms that are called into play during chronic high or low iodine intake lead to thyroid disease, particularly in certain predisposed individuals.

Evidence that TGF-beta can inhibit human T-lymphocyte proliferation through paracrine and autocrine mechanisms.

Transforming growth factor-beta (TGF-beta) has been documented as having an inhibitory effect on the proliferation and growth of human T-lymphocytes. We examined the relative contribution of both exogenous and endogenous TGF-beta to this inhibitory action. Purified human peripheral blood T-cells were cultured with Con A (0.2 microgram/ml), washed with methyl mannopyranoside, and then cultured in rIL-2 (5 U/ml) with or without TGF-beta (80 pM). Proliferation, as measured by uptake of tritiated thymidine at 72 hr, was inhibited by added active TGF-beta. Addition of neutralizing anti-TGF-beta antibodies at the initiation of culture abrogated the antiproliferative effects of TGF-beta. A mink lung cell bioassay was used to measure endogenous TGF-beta production by the T-cells following transient acidification of the supernatants to activate latent TGF-beta. T-lymphocytes cultured with rIL-2 alone produced low levels of TGF-beta, first detectable at 72 hr. The addition of (active) TGF-beta to these cultures resulted in earlier and higher levels of endogenously produced latent TGF-beta protein. This was reflected at the mRNA level as well. The exogenously added active TGF-beta appeared to be depleted during the culture period, presumably by the activated T-cells, which exhibited elevated levels of types I, II, and III TGF-beta receptors. The increase in TGF-beta protein levels was due to endogenous TGF-beta synthesis and secretion as supported by a capture assay using 35S-labeled culture supernatants. These findings indicate that both paracrine and autocrine mechanisms are involved in the inhibitory effects of TGF-beta on the proliferation of normal human T-lymphocytes and suggest that other TGF-beta-producing cells can augment production of TGF-beta by activated T-lymphocytes.

Hepatocyte membrane injury and bleb formation following low dose comfrey toxicity in rats.

Comfrey, a popular herbal remedy, contains hepatotoxic pyrrolizidine alkaloids and has been implicated in recent human toxicity. Although alkaloids from other plant sources have been extensively researched, studies on the hepatotoxic effects of comfrey alkaloids are scant. The effects of high dose comfrey toxicity have been studied and the present investigation was undertaken to identify changes associated with relatively low dose toxicity. Eight young adult rats were dosed weekly for six weeks with 50 mg/kg of comfrey derived alkaloids. The animals were dissected one week after the last dose and the livers examined by light and electron microscopy. Changes at the light microscopic level showed vascular congestion, mild zone 3 necrosis and loss of definition of hepatocyte cellular membranes. Extensive ultrastructural abnormalities were identified in the form of endothelial sloughing and the loss of hepatocyte microvilli. A striking finding was florid bleb formation on the sinusoidal borders of hepatocytes. Many blebs were shed into the space of Disse and extruded to fill, and sometimes occlude, sinusoidal lumina. Platelets were frequently found in areas of bleb formation. There was evidence of late damage in collagenization of Disse's space. Hepatocyte bleb formation is known to occur under a variety of pathological conditions but there is little to no information in the literature on the effects, if any, of bleb formation on fibrogenesis and the microcirculation and its role in the pathogenesis of liver disease. The pyrrolizidine alkaloids of comfrey may serve as an experimental tool to study the process of bleb formation and the intimate relationship between hepatocyte and sinusoidal injury in the liver.

Transforming growth factor-beta inhibits human T-cell proliferation through multiple targets.

This study investigates further the inhibitory effects of transforming growth factor-beta (TGF-beta) on human T-lymphocyte responses to mitogenic stimulation. T cells were stimulated either with mitogenic concentrations of PHA or with submitogenic concentrations of Con A followed by the addition of IL-2. DNA synthesis ([3H]thymidine incorporation) in both systems was inhibited by 60-69% in the presence of TGF-beta, with maximal reduction occurring on days 4 and 5 of culture. Cell surface expression of transferrin receptor (TfR) and IL-2 receptor-alpha (p55) were inhibited by 20-80% in the Con A/rIL-2 system and 20-45% in the PHA system in the presence of TGF-beta. In addition, mitogen-induced up-regulation of TfR and IL-2R mRNA levels were inhibited by TGF-beta. Finally, we investigated the effect of TGF-beta on the assembly of clathrin monomers into assembled coated pits and vesicles, and essential step in TfR and IL-2R alpha turnover. Stimulation of T cells using either mitogen system resulted in an increase in the level of assembled clathrin, which was almost completely inhibited by TGF-beta. These findings suggest that TGF-beta may act at several sites in mitogen-mediated proliferative pathways to contribute to the inhibition of T-cell proliferation.

Serum free thyroxine levels respond inversely to changes in levels of dietary iodine in the domestic cat.

Because of a perceived increase in the incidence of toxic multinodular goitres in cats in recent years, we investigated the iodine content of three varieties of commercial canned cat foods and studied the acute effects of 'ingestion of these preparations on urinary iodine excretion and serum free thyroxine levels in young, healthy cats. Ten castrated male cats were fed from a common source. The type of food was changed every 2 weeks. Urine and blood specimens were obtained weekly. Serum free thyroxine levels were determined and iodine concentrations in urine were assayed. The iodine content of the cats' food was also assayed. Food varieties of high, intermediate and low iodine content were fed for 2-week periods. There was a consistent, reciprocal relationship between the mean urinary iodine concentration and the mean serum free thyroxine level for each 2-week period. The difference in the mean serum free thyroxine concentrations for the high and low iodine intake periods was highly significant (p<0.01). When the serum free thyroxine level and the urinary iodine level for each cat at each collection throughout the 12-week study were analysed (66 paired results), a strong inverse correlation (r=0.59, p<0.01) was found. We concluded that the serum free thyroxine level in cats, as measured by a kit designed for human serum, is acutely responsive to changes in iodine intake.

Iodine content of commercially-prepared cat foods.

Twenty-eight varieties of commercially-available cat food (23 canned, 5 dried) were analysed for iodine. The iodine concentration varied from less than 0.37 micromol/kg to 41.8 pmol/kg, wet weight (less than 1.48 micromol/kg to 167 micromol/kg, dry weight). Excessive or insufficient iodine intake or wide swings in iodine intake over prolonged periods may contribute to thyroid disorders in cats.

Serum levels of free and bound testosterone in hyperthyroidism.

OBJECTIVE: The aim of this study was to improve knowledge about the relationships between free and bound forms of testosterone in serum and the major testosterone-binding proteins during hyperthyroidism. DESIGN: Nine men and 11 women were studied when hyperthyroid due to Graves' disease and again after at least 3 months of euthyroidism. MEASUREMENTS: The serum concentrations of free T3, free T4, TSH, sex hormone-binding globulin (SHBG), LH, progesterone and free, non-SHBG bound and total testosterone were determined. RESULTS: For both sexes, hyperthyroidism was associated with significant elevations of the mean total testosterone and sex hormone-binding globulin (SHBG) levels and significant depressions of the mean percentage and concentration of non-SHBG-bound testosterone and the mean percentage of free testosterone. For women, the mean free testosterone concentration was significantly lower during hyperthyroidism than during euthyroidism; no significant difference in mean free testosterone concentration was observed between hyperthyroid and euthyroid men. When the experimentally derived data were analysed according to a model based on the binding constants of testosterone with SHBG and albumin, the simulated results for each patient when hyperthyroid and euthyroid paralleled the actual results. However, the model consistently overestimated the actual amounts of non-SHBG-bound testosterone. There was a significant correlation between SHBG concentration and the severity of thyrotoxicosis as measured by the change in thyroid hormone levels between euthyroidism and hyperthyroidism. CONCLUSIONS: Our results support the following pathogenetic sequence: thyrotoxicosis leads to a rise in serum SHBG concentration which is accompanied by an increase in testosterone concentration, a fall in the concentration of non-SHBG-bound testosterone and little or no change in the concentration of free testosterone.

The management of Graves' disease in New Zealand: results of a national survey.

OBJECT: to compare treatment of Graves' disease in New Zealand with treatment in Europe and the United States of America (USA). METHODS: we circulated a questionnaire used in recent surveys in Europe and USA to all specialist physicians in New Zealand registered with the Medical Council. In the questionnaire a patient with uncomplicated Graves' disease was given as an index case, followed by eight clinical variations with regard to goitre size, severity, sex, age and previous treatment. RESULTS: two hundred and ninety-six (79%) out of 374 physicians responded to a preliminary letter asking whether they would be willing to participate in the survey. Of the respondents 71 (24%) saw more than two patients with Graves' disease per year and were included in the analysis (186 saw fewer than two cases per year and 39 failed to return questionnaires). For the index case, 55% of New Zealand respondents would treat with antithyroid drugs, 41% with radioiodine and 4% with surgery. For the index case and its variations the use of radioactive iodine by New Zealand physicians was greater than their European, but less than their American, counterparts. Surgery was infrequently recommended in any of the countries except for the patient with a large goitre, for whom 24% of New Zealand and 51% of European respondents would recommend subtotal thyroidectomy. CONCLUSION: we have demonstrated a spectrum of behaviour by physicians in the treatment of Graves' disease based on infrequent use of surgery and the willingness to use radioactive iodine instead of treatment with antithyroid drugs. New Zealand physicians appear to be more conservative in the use of radioiodine than their American, but less than their European counterparts.

Iodine intake and the seasonal incidence of thyrotoxicosis in New Zealand.

We explored a possible relationship between the seasonal variation in the incidence of thyrotoxicosis in our area and iodine intake, as assessed by measuring the 24-h urinary iodide excretion rate eight times at 3-month intervals in a group of normal subjects and in 992 outpatient specimens over a 2-year period (1988-1990). For the period 1978-1990, 139 cases of thyrotoxicosis were diagnosed during the warmer half of the year (November-April) and 100 cases during the cooler half (May-October). This difference was statistically highly significant (P = 0.013). A similar disproportionality in the incidence of thyrotoxicosis was observed between the warmer (57%) and cooler (43%) halves of the year for the period 1988-1990. During the 1988-1990 period there was no discernible seasonal variation in either the milk iodide concentration or in the cumulative mean 24-h urinary iodide excretion rates for the normal subjects or the outpatients. We conclude that the higher proportion of thyrotoxic patients diagnosed during the warmer 6-month period of the year in our area is best explained by the fact that symptoms tend to be less tolerable in warm weather. A comparison of our findings on 24-h urinary iodide excretion rates with data collected in our area 25 years ago suggested that iodine intake may have declined.

Once daily, low dose, short term antithyroid drug treatment of Graves' disease is followed by an unacceptably high relapse rate.

Thirty-six patients with hyperthyroid Graves' disease were treated with low doses of antithyroid drugs until thyroid function test results indicated euthyroidism or mild hypothyroidism (median treatment period three months, range 1.5-8 months). Less than one-half (42%) of the patients remained hyperthyroid after two months of treatment, but 21% were still thyrotoxic after three months of treatment. Of 32 patients who completed treatment and entered the observation period after treatment was withdrawn, 27 (84%) have relapsed, two have remitted for one year or more and three have been followed for less than one year without relapse. Although once daily, low dose, short term antithyroid drug treatment of patients with Graves' disease in the Wellington area satisfactorily controls the hyperthyroidism in the majority of cases, it is followed by an unacceptably high relapse rate.

A survey of the iodide concentration of human milk.

The iodide concentration of human milk from mothers living in the Wellington area and of six prepared infant formulae was measured. A total of 93 human milk samples were assayed, 14 from mothers of infants delivered at less than 35 weeks gestation and collected within 30 days of delivery (group A), 57 samples from mothers of infants delivered at 35 or more weeks gestation and collected within 60 days of delivery (group B) and 22 samples from mothers with infants aged greater than 60 days (group C). There was no significant (p greater than 0.05) difference between the means (SE) of groups A 1.14 mumol/L (0.20) and B 0.98 mumol/L (0.07). The mean for group C 0.39 mumol/L (0.03) was significantly less (p less than 0.05) than the means for both groups A and B. For groups A, B and C combined, there was a correlation (r = 0.44, p less than 0.01) between the milk iodide concentration and the iodide/creatinine ratio of a maternal urine specimen obtained immediately before or after the milk specimen. Formula milk preparations based on cow's milk contained higher concentrations of iodide than human milk.