Henry C. Ford

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

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.

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

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.

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

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.

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.

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

Effects of hyperthyroidism and radioactive iodine given to ablate the thyroid on the composition of whole stimulated saliva

OBJECTIVEu2003For many years there has been speculation about possible damage to the salivary glands following administration of ablative doses of radioactive iodine for treatment of hyperthyroidism. We have investigated the changes that occur in the composition of saliva in hyperthyroidism and after the administration of an ablative dose of radioactive iodine to hyperthyroid subjects.

Acidic Isoforms of Chorionic Gonadotropin in European and Samoan Women Are Associated With Hyperemesis Gravidarum and May Be Thyrotrophic

OBJECTIVEnThere 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.nnnPATIENTS AND DESIGNnWe enrolled 10 European and 10 Samoan women with HG and an equally sized non-hyperemetic, gestational stage matched control group.nnnMEASUREMENTSnWe 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).nnnRESULTSnThe 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.nnnCONCLUSIONSnAcidic 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.