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Biomedical subjects

S C Boyages

Publications and source records attributed to S C Boyages.

At least 19 recordsLinked to original sources
PubMed2005

Patterns of care as a risk factor for the development of vision-threatening diabetic retinopathy: a population-based matched case-control study using insurance claims (Medicare) data.

OBJECTIVES: To evaluate systematically the effectiveness of the primary healthcare system in Australia in preventing the development of advanced diabetes complications. METHODS: Diabetes patients (n = 4632) who had received their first laser photocoagulation treatment in 2000 were compared with a random sample of diabetes patients who had never received this treatment (n = 4632). Patterns of health care utilization were compared over a 7-year period (1993-1999) using the Australian Medicare database. RESULTS: There were significant differences in levels of healthcare utilization: cases were less likely to attend a general practitioner, from odds ratio (OR) = 0.21 (P < 0.0001) in 1993 to 0.53 (P < 0.0001) in 1999; less likely to be tested for HbA(1c), from OR = 0.24 in 1997 (P < 0.0001) to 0.38 in 1999 (P < 0.0001); for HDL-cholesterol, from OR = 0.017 (P < 0.0001) in 1999 to 0.04 (P < 0.0001) in 1993; and to attend specialists and consultant physicians, from OR = 0.25 (P < 0.0001) in 1994 to 0.44 (P < 0.0001) in 1999. The multivariate analysis emphasized the importance of timely diagnosis, HDL-cholesterol testing and optometry attendances in the prevention of advanced diabetes complications. CONCLUSIONS: The study supports the contention that healthcare utilization may be as important a determinant of health outcomes as clinical risk factors such as blood glucose control. This highlights the importance of early diagnosis and the need to address systemic barriers so as to increase primary care utilization for people at risk of advanced diabetes complications.

Adolescent↗
PubMed2001

Thyroid ultrasonography consistently identifies goiter in adults over the age of 30 years despite a diminished response with aging of the thyroid gland to the effects of goitrogenesis.

Iodine deficiency is a national health problem in India and we have recently reported on the severity of IDD in adults and children in Gujarat province. The aim of this study was to determine the utility of thyroid ultrasonography to detect goiter in adults from an iodine-deficient population of Gujarat. We studied 472 adults selected by random household surveys. Data were collected on height, body weight, mid-upper arm circumference, thigh circumference, triceps skinfold thickness, thyroid size (palpation and ultrasonography), and diet. Casual urine samples for iodine (UI) and blood spots for TSH estimation were obtained. Endemic goiter is a major public health problem in Gujarat State, India and is probably caused by multiple factors including iodine deficiency, malnutrition, and other dietary goitrogens. These results indicate that thyroid US consistently detects goiter in adults despite a diminished thyroidal response to variable goitrogenic stimuli.

Adult↗
PubMed2001

Study of biochemical prevalence indicators for the assessment of iodine deficiency disorders in adults at field conditions in Gujarat (India).

The main objective of this study was to assess the severity of iodine deficiency disorders (IDD) in the adult populations of the Baroda and Dang districts from Gujarat, western India using biochemical prevalence indicators of IDD. The other aim of this study was to establish a biochemical baseline for adequate iodine intake as a result of program evolution in the face of multiple confounding factors, like malnutrition and goitrogens responsible for goiter. A total of 959 adults (16-85 years) were studied from two districts (Baroda and Dang) and data was collected on dietary habits, anthropometric and biochemical parameters such as height, weight, urinary iodine (UI) and blood thyroid stimulating hormone (TSH). Drinking water and cooking salt were analyzed for iodine content. All subjects, irrespective of sex and district, showed median UI = 73 microg/L and mean blood TSH +/- SD = 1.59+/-2.4 mU/L. Seven per cent of the studied population had blood TSH values > 5 mU/L. Females in Baroda and males from Dang district were more affected by iodine deficiency as shown by a lower median UI. Mean TSH was significantly higher in women from both districts as compared to men (P = 0.001). The blood spots TSH values > 5 mU/L were seen in 20% of women from Dang. The normative accepted WHO values for UI and TSH for the severity of IDD as a significant health problem are not available for target population of adults. Urinary iodine normative limits and cut-offs are established for school-aged children. Blood spot TSH upper limit and cut-off values are available for neonate populations. The IDD has not been eliminated so far, as more than 20% of both male and female subjects had UI < 50 microg/L. Males were more malnourished than females in both districts (P < 0.05). Pearl millet from Baroda contained flavonoids like apigenin, vitexin and glycosyl-vitexin. Dang district water lacked in iodine content. Iodine deficiency disorder is a public health problem in Gujarat, with the Baroda district a new pocket of IDD. High amounts of dietary flavonoids in Baroda and Dang, malnutrition and an additional lack of iodine in Dang water account for IDD.

Adolescent↗
PubMed2001

Re-emergence of iodine deficiency in Australia.

Iodine is an essential nutrient for human growth and development. The thyroid gland is dependent upon iodine for production of thyroid hormone. It is a common perception that iodine deficiency is not a major public health concern in mainland Australia, with sporadic studies carried out about a decade ago showing average urinary iodine excretion levels of around 200 microg/day. Recent evidence, however, has shown that the consumption of iodine is declining in Australia. A similar situation has occurred in the USA. The present study was designed to evaluate the urinary iodine excretion (UIE), as the indicator of iodine nutrition, in samples obtained from various demographic groups in the Sydney metropolitian area, namely: schoolchildren, healthy adult volunteers. pregnant women and patients with diabetes. Urinary iodine in spot urine sample was measured in a Technicon II autoanalyser using an in-house, semiautomated method. The results in this communication show that all four study groups had the median UIE below 100 microg/L. the criteria set by the World Health Organization for iodine repletion, and confirm what has been described previously, that iodine deficiency has reemerged in Sydney, Australia. One of the major causes of the reduced iodine intake is the reduction of iodine in milk since the dairy industry replaced iodine-rich cleaning solutions with other sanitisers. Secondly, less than 10% of the population are currently using iodised salt. A national survey into the iodine nutrition status in Australia is urgently required as part of the establishment of a systematic surveillance and legislation is required to iodise all edible salt.

Adolescent↗
PubMed2001

Insulin secretion and insulin sensitivity are normal in non-diabetic subjects from maternal inheritance diabetes and deafness families.

BACKGROUND: The pathophysiological mechanism of diabetes mellitus in the presence of the 3243 A-G tRNALEU(UR) mitochondrial DNA mutation is thought to result from deficient insulin secretion. However, few subjects with normal glucose tolerance have been studied to determine the sequence of events resulting in the development of diabetes mellitus. AIM: To determine whether abnormalities of insulin sensitivity, insulin secretion or glucose effectiveness are present in non-diabetic subjects with the 3243 A-G tRNALEU(UUR) mitochondrial DNA mutation. METHODS: Twelve non-diabetic subjects with the mutation were compared with 12 controls, matched for age and anthropometric parameters, using both oral and intravenous glucose tolerance tests, the latter with Minimal Model analysis. RESULTS: Following an oral glucose load we found significantly higher blood glucose levels at 90 min and 120 min and significantly higher insulin levels at 120 min and 180 min in non-diabetic subjects with the mutation but no difference in the insulinogenic indices at 30 min and 180 min. From the intravenous glucose tolerance test there was no difference in overall glucose tolerance, insulin sensitivity, first- or second-phase insulin secretion, proinsulin secretion or glucose effectiveness. Insulin-independent glucose disposal was increased in subjects with lower insulin sensitivity and declined with increasing age in subjects with the mutation but not in controls. CONCLUSIONS: While there appear to be subtle defects of glucose handling in non-diabetic subjects with the 3243 mutation, these could not be explained by differences in insulin sensitivity or secretion.

Autoantibodies↗
PubMed2001

Impact of protein energy malnutrition on thyroid size in an iodine deficient population of Gujarat (India): Is it an aetiological factor for goiter?

OBJECTIVE: To assess the severity of protein energy malnutrition (PEM) in iodine deficient subjects and to assess the impact of PEM on thyroid size. METHODS: 1002 subjects (530 school-aged children and 472 adults) were assessed for PEM by direct anthropometric measurements of height, weight, triceps skinfold (TSF) thickness, mid upper arm circumference (MUAC) and thigh circumference (TC), and derived indices of body surface area (BSA), body mass index (BMI), and Z-scores for weight-for-age (WAZ), height-for-age (HAZ), and weight-for-height (WHZ). Severity of PEM was based on the World Health Organization (WHO) criteria and the threshold on the Waterlow classification. Thyroid size was measured by ultrasonography to determine the thyroid volume (TV). Linear regression analysis was performed between TV and anthropometric parameters. RESULTS: Children had severe PEM as evident from the WHO percentage prevalence of stunting (HAZ<-2SD)=64% (where <-2SD is the Z-score deficit), wasting (WHZ<-2SD)=43%, underweight (WAZ<-2SD)=82% and BMI<16 kg/m=90%. Waterlow classification showed that children were either stunted or wasted, or stunted and wasted, or stunted and obese. Nearly 100% (529/530) of the children had goiter as evidenced from enlarged TV-for-BSA when compared with the WHO reference. There was a weak but statistically significant (P<0.05) positive correlation between TV and BSA, weight, height, MUAC, TC and HAZ but a negative correlation between TV and WHZ, BMI and TSF (r=-0.1-0.2). Adults had PEM as evident from BMI<18.5 kg/m in 54% subjects. Median MUAC=22.7 cm reveals prolonged severe PEM. Eighty-two percent had enlarged TV (>20 ml). There was a significant (P=0.01) negative correlation between TV and MUAC. CONCLUSIONS: (i) The severity of acute (wasting) and chronic (stunting) PEM is very high in Gujarati children. They are stunted or wasted, or stunted and wasted, or stunted and obese. Gujarati adults are thin with low protein and fat reserves. (ii) Anthropometric parameters showed a significant (P<0.001) correlation (r=0.1-0.2) with thyroid size. (iii) Higher prevalence of goiter may be due to macro-nutrient malnutrition (PEM) in the face of micro-nutrient malnutrition (iodine deficiency disorders, IDD).

Adolescent↗
PubMed2000

Thyroid ultrasound is the best prevalence indicator for assessment of iodine deficiency disorders: a study in rural/tribal schoolchildren from Gujarat (Western India).

OBJECTIVES: (i) To assess the severity of iodine deficiency disorders (IDD), (ii) to determine the aetiology of IDD in Gujarat, (iii) to identify the best prevalence indicator of IDD, and (iv) to compare thyroid volume (TV) results with the WHO International reference. METHODS: Five hundred and thirty schoolchildren (6-15 years) were studied from two districts (Baroda and Dang) and data were collected on dietary habits and parameters such as height, weight, thyroid size by palpation and ultrasonography, urinary iodine (UI), and blood thyroid stimulating hormone (TSH). Drinking water was analyzed for iodine content and food articles for goitrogens. RESULTS: In Gujarat children median UI (interquartile range)=56 (30-96)microg/l, mean TSH=1.71 +/- 2.10mU/l, goiter by palpatio n = 30%, and median TV = 27.8 (23-35)ml. Females had lower median UI (48 (27-82) microg/l) and higher mean TSH levels (2.0 +/- 2.5mU/l) than males. Applying the WHO ultrasonography reference to Gujarat children resulted in an enlarged TV-for-body surface area in almost 100% of subjects. Ninety-nine percent of females and 95% of males had enlarged TV-for-age. Three to eight times larger TV were seen in all subjects as compared with European children. Dang children were severely malnourished. Flavonoids like vitexin, glucosyl vitexin and apigenin were detected in pearl millet. Apigenin was never identified in pearl millet. Dang district water was lacking in iodine content. CONCLUSIONS: IDD is a severe public health problem in Gujarat. Baroda district is a new pocket of IDD. High amounts of dietary flavonoids in Baroda and Dang districts, and lack of iodine in Dang water, account for IDD. TV measurement by ultrasound is the best prevalence indicator of IDD.

Adolescent↗
PubMed1999

Beyond evidence-based guidelines to implementation: a model for integrating care for people with diabetes.

There is a growing realization in the health system that integration of effort may be the best way of ensuring optimal outcomes of management both for clinicians and for people using the health system. It is also hypothesized that the impact of diabetes (chronic disease) and its sequelae could be reduced by the provision of well-organized care, based on agreed evidence-based guidelines for best practice, incorporating patient education and early detection of complication. This paper defines the characteristics of an integrated model of providing care to people with diabetes.

Community Health Planning↗
PubMed1999

Amiodarone compared with iodine exhibits a potent and persistent inhibitory effect on TSH-stimulated cAMP production in vitro: a possible mechanism to explain amiodarone-induced hypothyroidism.

Amiodarone (AMD) is a powerful anti-arrhythmic drug used for the treatment of a wide variety of cardiac arrhythmias and its most striking feature is its high iodine content. Thyroid dysfunction is a limiting side-effect of the drug and both AMD-induced hypothyroidism (AIH) and AMD-induced thyrotoxicosis (AIT) are reported. To examine the hypothesis that altered bioavailability of iodine is a contributing event in the pathogenesis of AIH, we compared the effects of AMD and inorganic iodine in vitro on events involved in the process of thyroid autoregulation. FRTL-5 cells and JP26 CHO cells (transfected with the human TSH receptor) were exposed to AMD or NaI in the presence of TSH, and cAMP production was measured as an indicator of cellular function. Forskolin and cholera toxin were also used to determine the possible target sites of AMD and iodide. Our results indicated that there was a difference between the effects of AMD versus those of physiological doses of iodide. The inhibitory effects of AMD occurred at lower concentrations of iodide than those seen in the NaI-treated cells. The effects of AMD were irreversible indicating a possible persistence of the Wolff-Chaikoff effect due to a constant high intracellular iodide level. The inhibitory effects of AMD (also seen at supraphysiological doses of iodide) were partially overcome by forskolin but not by cholera toxin indicating an effect on TSH receptor interactions with the other signal transduction elements such as G proteins and adenylate cyclase. The persistence of the Wolff-Chaikoff effect through loss of autoregulation may be a mechanism of the observed hypothyroidism in some patients taking AMD. The combined effects of the constant release of iodide together with the drug toxicity may be the mechanism for the observed effects.

Amiodarone↗
PubMed1998

Does mitochondrial genome mutation in subjects with maternally inherited diabetes and deafness decrease severity of diabetic retinopathy?

Two types of retinopathy, diabetic and pigmentary, may be seen in subjects with maternal inheritance diabetes and deafness. The potential for interactions between the two retinopathies has not been explored. The mitochondrial mutation may affect development of diabetic retinopathy in subjects with MIDD by altering normal pathways of glucose metabolism. We identified five unrelated MIDD kindreds with 61 living maternal line family members. Twenty-three of the family members, 12 with diabetes mellitus and 11 without volunteered to be studied. Subjects were graded for severity of diabetic retinopathy and presence or absence of pigmentary retinopathy after slit lamp biomicroscopy, retinal photography of seven standard fields and fluorescein angiography. Blood was taken, in the fasted state, from MIDD subjects (duration of diabetes 17.0+/-6.9 yr) and non-diabetic subjects with the mutation, for assay of sorbitol and glucose and values compared with diabetic and non-diabetic control subjects without the mutation. Diabetic retinopathy was absent in 9/12 subjects (75%), with 3 having mild non-proliferative retinopathy. No one had cataract. Red blood cell sorbitol levels, adjusted for ambient blood glucose, were significantly lower in MIDD subjects compared with diabetic subjects (1.16+/-0.5 cf. 2.03+/-1.1, x 10(-3) g mmol(-1), p=0.04). Pigmentary retinopathy was present in 15 of 23 subjects, of whom 13 had some abnormality of glucose tolerance. Abnormal glucose tolerance was strongly associated with the development of pigmentary retinopathy (odds ratio 19.5, p=0.008). In conclusion, there appears to be a decreased prevalence of diabetic retinopathy and cataract in MIDD, which we propose is due to reduced glucose metabolism by the polyol pathway. Abnormal glucose tolerance increases the clinical expression of pigmentary retinopathy in subjects with a mitochondrial genome mutation. A greater understanding of the metabolic effects of mitochondrial DNA mutations has the potential to give insight into the mechanisms of diabetic retinopathy and other complications of diabetes mellitus.

Adult↗
PubMed1998

Cochlear origin of hearing loss in MELAS syndrome.

There have been few studies investigating the mechanism and nature of the hearing loss that occurs in the mitochondrial disorders. We studied 18 patients with the MELAS A3243G point mutation from four different kindreds. Pure tone audiometry, speech discrimination testing, acoustic reflexes, tympanometry, and brain stem auditory evoked responses were performed to localize the site of pathology in the auditory pathways. In 12 patients, we performed electrocochleography and otoacoustic emissions to assess cochlear involvement. Neuroimaging and promontory nerve stimulation were performed to exclude retrocochlear pathology. Audiological testing confirmed sensorineural hearing loss in 14 of the 18 patients studied; hearing loss was usually gradual in onset, was symmetrical, and initially affected the higher frequencies. In some patients, there were features that distinguished the hearing loss from presbyacusis, including a young age at onset, asymmetrical involvement, stepwise progression, and partial recovery. We treated one patient who had profound bilateral hearing loss with cochlear implantation; this restored good functional hearing. Hearing loss in MELAS syndrome appears to be due to dysfunction of the cochlea, probably resulting from metabolic failure of the stria vascularis and outer hair cells. Cochlear implantation is a therapeutic option worth considering in those patients who become deaf.

Adolescent↗
PubMed1997

Expression of beta2-thyroid hormone receptor in euthyroid and hypothyroid rat pituitary gland: an in situ hybridization and immunocytochemical study.

Recently, we have shown an extended distribution pattern of the TR-beta2 isoform in specific sites of rat brain which may be indicative that the localization of this receptor also confers functional specificity. The beta2 thyroid hormone receptor (TR-beta2) is by far the most abundant isoform in the pituitary, although transcripts of TR-alpha and TR-beta1 genes have been reported in developmental and adult rat pituitary gland. Using both in situ hybridization histochemistry (ISH) and immunocytochemistry, we mapped the expression of beta2 thyroid hormone receptor mRNA and protein in euthyroid and hypothyroid adult rat pituitary, particularly in relation to the thyrotrope population. TR-beta2 mRNA localization by ISH showed an anteromedial spatial distribution pattern in euthyroid rat anterior pituitary gland. This localization coincided with the immunostaining pattern for thyrotropes. TR-beta2-immunoreactive cells showed strongly positive signals in the nuclei. Hypothyroidism, induced by propylthiouracil (PTU), abolished the specific localization of TR-beta2 mRNA and upregulated the transcription of TR-beta2 mRNA in vivo and in vitro. Image analysis revealed that the optical density signals within hypothyroid rat pituitary were significantly stronger (2.6-fold) compared with euthyroid counterparts. This correlated strongly with an increased number and staining of TR-beta2 protein positive cells, demonstrating both nuclear and cytoplasmic staining. In response to thyroid hormone deficiency, there was also a marked percentage increase in the thyrotrope population from 10 to 20% of anterior pituitary cells to approximately 80%. In conclusion, these results demonstrate the specific localization of TR-beta2 to the anterior pituitary, especially to the thyrotrope population, and its regulation by thyroid hormone. Hypothyroidism leads to an upregulation of TR-beta2 mRNA and protein in the anterior pituitary, explained not only by an absolute increase in the percentage of thyrotropes but increased expression of TR-beta2 mRNA and protein per cell. These data allude to the TR-beta2 isoform playing a critical role in thyroid hormone-dependent TSH gene expression, although contributions from the other TR isoforms may still remain important.

Animals↗
PubMed1997

The thyroid gland in acromegaly: an ultrasonographic study.

OBJECTIVE: An association between acromegaly and goitre is well recognized. We have studied the incidence and morphology of goitre in acromegaly, and examined the role of IGF-I and TSH in goitre pathogenesis. DESIGN AND SUBJECTS: Thirty-seven subjects with acromegaly, active or in remission, were assessed by ultrasound to determine thyroid volume (TV) and morphology, and compared with normal controls. Nine subjects with acromegaly were also studied again following treatment with octreotide for 1 year. RESULTS: Compared with controls, TV was greater (28.7 +/- 18.3 ml vs 5.4 +/- 2.6 ml, P < 0.001) and IGF-I levels were higher (62.0 +/- 34.8 nM vs 28.9 +/- 10.9 nM, P < 0.001) in subjects with acromegaly. Those with active disease tended to have larger glands (30.0 +/- 17.2 ml vs 22.2 +/- 16.7 ml, P = 0.18). The overall incidence of goitre was 92%. Twenty-seven subjects (73%) had nodules or heterogeneous thyroid echotexture. Subjects with nodular goitre had a longer duration of acromegaly than those with homogeneous glands (12.1 +/- 5.7 vs 7.6 +/- 4.0 years, P = 0.032). Those with nodular glands also had larger goitres than those with homogeneous glands (35.2 +/- 18.8 ml vs 19.5 +/- 11.9 ml, P = 0.032). Thyroid volume correlated with IGF-I levels (r2 = 0.38, P = 0.002) and body mass index (r2 = 0.24, P < 0.001), and there was an inverse relationship with TSH levels (r2 = 0.46, P = 0.032). Patients studied again after treatment with octreotide for 1 year had a reduction in TV from 32.6 +/- 16.1 to 27.6 +/- 17.0 ml (P = 0.041). CONCLUSIONS: This study confirms that goitre is a common finding in acromegaly. Our findings suggest that early in the course of the disease, diffuse goitre occurs. Subsequently, thyroid autonomy and nodule formation develop, and further growth may occur independent of TSH. With control of GH hypersecretion, a reduction in thyroid size occurs, but this may be limited by the extent of thyroid nodularity.

Acromegaly↗