Biomedical subjects

J C Blair

Publications and source records attributed to J C Blair.

17 recordsLinked to original sources

PubMed2005

IGFs and IGFBPs in GH insensitivity.

IGF-I, IGFBP-3 and ALS are GH-dependent peptides and their production is disturbed in states of GH insensitivity. This chapter explores the relative degrees of IGF-I, IGFBP-3 and ALS deficiency across the spectrum of GH insensitivity. In classical GH insensitivity syndrome (GHIS), known as Laron syndrome, due to GH receptor (GHR) deficiency, serum IGF-I, IGFBP-3 and ALS are severely reduced with inability to produce these peptides during an IGF-I generation test. Across the spectrum of severity of GHR defects, some patients have short stature and normal facial appearance, so-called partial or non-classical GH insensitivity. In these cases the IGF-I, IGFBP-3 deficiency is less severe. A positive relationship exists between height SDS and IGFBP-3 SDS (r2 = 0.45, p < 0.001) in patients from the European series with GHIS. In a new series of GHIS cases (n = 36) there was a significant difference in IGFBP-3 and ALS (p < 0.05) between classical (n = 25) and non-classical cases (n = 11). IGF-I, IGFBP-3 and ALS were significantly higher (p < 0.05) in pubertal compared with pre-pubertal subjects in the same series. In idiopathic short stature (ISS), heterozygous mutations of the GHR may have a dominant negative effect. ISS patients have lower IGF-I levels than the normal population. In 21 cases, mean IGF-I SDS was -1.39 (-2.4 to -1.16) and IGFBP-3; -0.45 (-1.13 to 0.38). However, IGF-I and IGFBP-3 responses in the IGF-I generation test were generally normal. In acquired GHI due to chronic illness such as Crohn's disease, juvenile arthritis and cystic fibrosis, IGF-I deficiency is present, although IGFBP-3 is usually normal. In summary, assessment of IGF-I, IGFBP-3 and ALS contributes to diagnosis in GH insensitivity states. In our experience, IGF-I is more sensitive to disturbance of GH action that IGFBP-3, however in severe GHIS cases, IGF-I is usually undetectable and measurement of IGFBP-3 is valuable as a guide to the severity of the biological defect.

Biomarkers↗

PubMed2004

Standard and low-dose IGF-I generation tests and spontaneous growth hormone secretion in children with idiopathic short stature.

OBJECTIVE: Abnormalities in the GH-IGF-I axis, consistent with GH insensitivity (GHI), have been reported in some patients with idiopathic short stature (ISS). The standard IGF-I generation test (IGFGT) has not demonstrated mild GHI in subjects with ISS. The aim of this study was to investigate the GH-IGF-I axis in ISS by performing standard and novel low-dose IGFGTs together with determination of spontaneous GH secretion. PATIENTS AND METHODS: Twenty-one (17 male) prepubertal children with ISS, mean age 8.3 years (4.5-12.2), mean height -3.48 SD (-5.40 to -1.79), mean peak GH to provocation with glucagon/clonidine 32.3 mU/l (14.1-66.0) were studied. Serum IGF-I and IGFBP-3 levels were measured during standard (GH 0.033 mg/kg/day x 4) and low (GH 0.011 mg/kg/day x 4) dose IGFGTs at 0, 12, 36 and 84 h. The low-dose IGFGT was performed in seven naive GH-deficient patients (4 male), mean age 8.5 years (range 4.1-11.1). Determination of spontaneous 24-h GH secretion was performed in the 21 ISS patients. RESULTS: Basal IGF-I and IGFBP-3 standard deviation scores (SDS) in ISS patients were -1.39 (-2.4-1.16) and -0.45 (-1.13-0.38), respectively, IGF-I being lower than IGFBP-3 (P < 0.0001). IGF-I increased in the standard IGFGT at 12 h (P < 0.005), 36 h (P < 0.001) and 84 h (P < 0.001); maximal increment 1.54 (-0.32-3.48), and in the low-dose test at 12 h (P < 0.005), 36 h (P < 0.001) and 84 h (P < 0.005); maximal increment 0.53 (0.08 to -1.23). IGFBP-3 SDS increased in the standard IGFGT at 36 h (P < 0.01) and 84 h (P < 0.001); maximal increment 0.72 (-0.44-1.96), and in the low-dose test at 84 h (P < 0.005); maximal increment 0.33 (-0.08-0.87). Five/19 patients with an IGF-I response > 2 x coefficient of variation (CV) of assay in the standard test failed to respond in the low-dose test, suggestive of mild GHI. In GH-deficient patients, IGF-I increased at each time point (P < 0.05) and IGFBP-3 at 36 h (P < 0.05). Mean GH secretion, expressed in SDS, compared with 66 normal stature controls was: basal GH -0.48 (-0.84-0.93), height of GH peaks compared with zero -0.36 (-1.26-1.51) (both P < 0.05), total GH secretion -0.76 (-1.22-0.42), total GH secretion above baseline -0.67 (-1.21-0.94) (both P < 0.01). CONCLUSIONS: In children with ISS, basal IGF-I and IGFBP-3 SDS values were below the mean, IGF-I showing a greater response in both IGFGTs. In the standard IGFGT, the IGF-I increase at 36 h was equal to that at 84 h. The low-dose IGFGT, in combination with the standard test, may identify patients with mild GHI.

Case-Control Studies↗

PubMed2002

Neonatal thyrotoxicosis and maternal infertility in thyroid hormone resistance due to a mutation in the TRbeta gene (M313T).

We report two unusual cases of resistance to thyroid hormone (RTH) in one family. The first case, a male infant, had clinical features of thyrotoxicosis in the neonatal period. In the fourth week of life weight gain was poor despite a daily intake of standard infant formula almost double the infant's estimated requirements. At this time serum free T4 (fT4) was 60.7 pmol/l (Normal range [NR] 11-25 pmol/l) and TSH was inappropriately normal at 1.8 mU/l (NR 0.3-4.0 mU/l). The infant responded clinically and biochemically to propylthiouracil (PTU) at a dose of 10 mg/kg/day. Following 27 days of treatment serum fT4 was 22.6 pmol/l and TSH had risen to 24.9 mU/l. As the infant was thriving treatment was discontinued. The infant, now aged 6 months old, remains clinically euthyroid and developmentally normal off treatment. The infant's mother, from whom he had inherited a mutation of the thyroid receptor beta (TRbeta) gene (M313T), presented earlier with secondary infertility and clinical features of thyrotoxicosis. Treatment with PTU restored her fertility and she spontaneously conceived. In the subsequent pregnancy, clinical and biochemical features of RTH improved, and she gave birth to a small but healthy female infant. In the next pregnancy, resulting in the birth of the affected male infant, clinical and biochemical features of RTH worsened, and high doses of PTU were required to maintain a clinically euthyroid state. To our knowledge, these are the first case reports of RTH associated with added features of a hypermetabolic state in infancy and secondary infertility.

Adult↗

PubMed2001

Growth abnormalities associated with adrenal disorders and their management.

Linear growth can be disturbed in paediatric adrenal disease associated with endocrine hypo- or hyperfunction. Tall stature is a feature in some patients with adrenocorticotropic hormone resistance syndromes and short stature is recognized in the IMAGe (intrauterine growth retardation, metaphyseal dysplasia, adrenal hypoplasia congenita and genital anomalies) association. In autoimmune Addison's disease, growth is usually normal. In congenital adrenal hyperplasia, height may be compromised by advanced skeletal maturation or by suppressed growth, particularly in the neonatal period due to excess glucocorticoid treatment. In virilizing adrenal tumours, height is increased at diagnosis, but after surgical cure final height is usually in the normal range. In Cushing's disease, height was abnormally short in 50% of patients at presentation. After successful treatment, spontaneous catch-up growth was not seen. This led to a diagnosis of growth hormone (GH) deficiency in 80% of patients. With GH replacement, catch-up growth and long-term benefit occurred. Disturbance of linear growth is an important feature of many patients with adrenal disorders in childhood. Assessment of its pathogenesis and careful management are necessary to ensure optimal final adult height.

Adrenal Gland Diseases↗

PubMed2001

Growth hormone insensitivity: pathophysiology, diagnosis, clinical variation and future perspectives.

The study of genetic growth hormone (GH) insensitivity is an evolving field. GH insensitivity syndrome (GHIS), otherwise known as Laron syndrome, is a heterogeneous disorder. Biochemical features consist of severe insulin-like growth factor I (IGF-I) and IGF-binding protein 3 (IGFBP-3) deficiency and elevated GH secretion. In a heterogeneous 'European' cohort of GHIS patients, features varied from classical to moderate abnormalities of phenotype and endocrine disturbance. A study of facial features within this series showed that a mild subgroup existed with normal facies, mild short stature and moderate biochemical abnormalities. Overlap with idiopathic short stature (ISS) exists, with heterozygous mutations of the GH receptor demonstrated to cause impaired growth. This 'partial' GHIS has not yet been defined endocrinologically. GH sensitivity, measured by IGF-I and IGFBP-3 responses in the IGF-I generation test, may reveal abnormalities in ISS, although it is likely that the dose of recombinant human GH and frequency of sampling in the test need to be modified.

Body Height↗

PubMed1998

Five "C's" of successful startups.

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Biotechnology↗

PubMed1994

Autonomy of audiologists in educational settings.

Professional autonomy continues to be an issue of major concern for practicing audiologists. Members of the Educational Audiology Association completed a written survey covering the amount of independence and authority they experience when employed in an educational setting. Four areas were explored: scope of practice; referral procedures; assessment and management activities; and employment conditions. Responses indicated that educational audiologists have a great deal of autonomy in matters relating to the scope of their practice and the implementation of daily activities. Autonomy in the area of employment conditions was much less widespread. This report provides a detailed description of the survey responses, conclusions, and implications for future training needs for audiologists who may be employed in an educational setting.

Audiology↗

PubMed1993

Screening procedures used to identify children with hearing loss.

This study focused on the hearing-screening procedures used to identify children who have hearing losses who were later enrolled in SKI*HI parent/infant programs throughout the country. Responses to a questionnaire for 1,404 children indicated that although auditory brainstem response (ABR) technology provided the lowest mean identification age, informal hearing-screening procedures (parental suspicion and referral) were the procedure of identification for 80% of the children. The data suggest that formal screening programs are not presently locating the vast majority of infants who have hearing losses. Recommendations for professional and parental education in the area of hearing-loss screening are provided.

Age Factors↗

PubMed1988

Modified assay for true and apparent metabolisable energy based on tube feeding.

1. To improve the accuracy with which true metabolisable energy (TME) values of feedingstuffs are determined, a modification to the assay based on tube-feeding is proposed. 2. To ensure that the gastrointestinal tracts of the experimental birds are as empty as possible at the start of the assay it is recommended that the normal food is withdrawn 48 h before tube-feeding. 3. In order to partly alleviate the effects of starvation, all birds are given two doses of 25 g glucose (as an aqueous solution) about 40 and 16 h before tube-feeding. Birds, from which endogenous energy losses are to be derived, are fed 50 g glucose rather than given no food. 4. All birds are given 50 ml water by tube about 32 h after feeding to overcome any effects induced by low water intake. 5. A comparison of the two procedures with 8 feedingstuffs showed that the mean coefficient of variation was reduced from 5.5% to 1.5% for TME and from 4.7% to 1.8% for TME.

Animal Feed↗

PubMed1986