Thyroid hormone: old hormone, new insights

Thyroid hormone mediates its many actions by binding to thyroid receptors which are ligand-dependent nuclear transcription factors bound to specific DNA sequences known as thyroid hormones response elements. There are three isoforms of the thyroid hormone receptor, namely TR, TRB 1 and TRB 2, which differ in their tissue distribution and transcriptional activity. Resistance to thyroid hormone (RTH) is a dominantly inherited condition which occurs when an affected individual harbours a mutation in one allele of the thyroid hormone receptor beta gene (TRB 1 and B2). Most affected patients exhibit elevated thyroid hormone concentrations associated with inappropriate secretion of thyrotropin (TSH). The clinical presentation of these patients is variable. Patients with generalised RTH exhibit varying degrees of peripheral insensitivity to thyroid hormone which manifests itself in some families as growth retardation and learning disabilities. In contrast, individuals with pituitary resistance present with signs and symptoms of thyrotoxicosis. To further elucidate the roles of these mutant receptors on the pituitary-hypothalamic thyroid axis, we have developed a transgenic mouse model of RTH by expressing a mutual thyroid hormone receptor (TRB 1) selectively in the pituitary. The mice developed profound pituitary resistance to thyroid hormone as demonstrated by markedly elevated baseline non T3 suppressible, serum TSH and pituitary TSHB and rnRNA. Paradoxically serum T4 levels were normal suggesting bioinactive TSH. The reduced biologic activity of the TSH in transgenic mice was reversed by throtropin releasing hormone (TRH) administration which resulted in markedly elevated T4 concentrations intransgenic but not in wild type mice.(AU)

A cross-sectional prevalence study of the protozoan and helminth infections in school children 6-12 years of age in Grenada

Data on the public health importance of intestinal parasites in Grenada have not been available for over 60 years and this study aimed to redress this information gap. Between May and June 1999, a cross-sectional point prevalence study of intestinal protozoans and helminths was carried out in school children aged 6-12 years of age in three schools in St George's Parish, Grenada. After receiving informed consent, a single stool sample was obtained which was immediately aliquoted and samples stored in either the refrigerator or freezer. The refrigerator sample was processed by a salt flotation concentration technique. The frozen sample was analysed by ELISA assay for antigens of intestinal protozoa. A total of 315 samples was collected. For protozoans, prevalence rates of 36, 12 and 3 percent were obtained for Giardia lamblia, Entamoeba histolytica and Cryptosporidium parvum, respectively. For helminths, prevalence rates were 0.4, 1.3, 5.3 and 1.4 percent for hookworm, Enterobius vermicularis, Trichuris trichuria and Ascaris lumbricoides, respectively. Protozoans are prevalent in Grenadians school children but helminths are not as common. These differences in prevalence rates may reflect the easy availability of broad spectrum antihelmintics whilst drugs for protozoan infections are obtained by prescription only. The dramatic difference in the prevalence of intestinal helminths from earlier in the 20th century may also reflect a considerable improvement in the socio-economic status of the population. (Au)

Diabetic admissions at the Queen Elizabeth Hospital, Barbados - does the timing of primary care contact make a difference? - abstract

The Queen Elizabeth Hospital (QEH) is the major secondary and tertiary health care facility in Barbados, and patients who reach this hospital either present directly to the Accident and Emergency Department (A+E), or are referred by physicians. Over a six-month period all diabetic admissions to the hospital were identified, each patient was interviewed and examined, and hospital progress and outcome recorded. Of the 539 patients identified, 201 (37 percent) came directly to the A+E, while 338 (63 percent) had been referred to hospital. Three hundred and sixty-two (69 percent) had seen a physician within three months of admission. The main reasons for admission were the diabetic septic foot (33 percent), followed by heart failure (13 percent) and acute myocardial infarct 12.5 percent. Because the diabetic septic foot is considered a largely preventable problem, the high admission rate suggests that preventive care, assessment and management at the primary care level are inadequate. Patients who visited their primary care physicians within three months of admission, but nevertheless ended up in hospital, had lower mortality rates but prolonged hospital stays (AU)