Prevention of Growth Failure in Turner Syndrome: Long-Term Results of Early Growth Hormone Treatment in the "Toddler Turner" Cohort

INTRODUCTION

In the randomized "Toddler Turner" study, girls who received growth hormone (GH) starting at ages 9 months to 4 years (early-treated [ET] group) had marked catch-up growth and were 1.6 ± 0.6 SD taller than untreated (early-untreated [EUT]) control girls after 2 years. However, whether the early catch-up growth would result in greater near-adult height (NAH) was unknown. Therefore, this extension study examined the long-term effects of toddler-age GH treatment on height, pubertal development, and safety parameters.

METHODS

Toddler Turner study participants were invited to enroll in a 10-year observational extension study for annual assessments of growth, pubertal status, and safety during long-term GH treatment to NAH for both ET and EUT groups.

RESULTS

The ET group was taller than the EUT group at all time points from preschool to maturity and was significantly taller at the onset of puberty (p = 0.016), however, the difference was not significant at NAH. For the full cohort (ET + EUT combined, n = 50) mean (± SD) NAH was 151.2 ± 7.1 cm at age 15.0 ± 1.3 years. NAH standard deviation score (SDS) was within the normal range (>-2.0) for 76% of ET and 60% of EUT subjects (68% overall) and correlated strongly with height SDS at GH start (r = 0.78; p < 0.01), which in turn had a modest inverse correlation with age at GH start (i.e., height SDS declined with increasing age in untreated girls [r = -0.30; p = 0.016]). No new safety concerns arose.

CONCLUSION

Although the ET group was taller throughout, height SDS at NAH was not significantly different between groups due to catch-down growth of ET girls during lapses in GH treatment after the Toddler study and similar long-term GH exposure overall. Early initiation of GH by age 6 years, followed by uninterrupted treatment during childhood, can prevent ongoing growth failure and enable attainment of height within the normal range during childhood, adolescence, and adulthood.

Altered Brain Structure in Infants with Turner Syndrome

Turner syndrome (TS) is a genetic disorder affecting approximately 1:2000 live-born females. It results from partial or complete X monosomy and is associated with a range of clinical issues including a unique cognitive profile and increased risk for certain behavioral problems. Structural neuroimaging studies in adolescents, adults, and older children with TS have revealed altered neuroanatomy but are unable to identify when in development differences arise. In addition, older children and adults have often been exposed to years of growth hormone and/or exogenous estrogen therapy with potential implications for neurodevelopment. The study presented here is the first to test whether brain structure is altered in infants with TS. Twenty-six infants with TS received high-resolution structural MRI scans of the brain at 1 year of age and were compared to 47 typically developing female and 39 typically developing male infants. Results indicate that the typical neuroanatomical profile seen in older individuals with TS, characterized by decreased gray matter volumes in premotor, somatosensory, and parietal-occipital cortex, is already present at 1 year of age, suggesting a stable phenotype with origins in the prenatal or early postnatal period.

Cleft palate and hypopituitarism in a patient with Noonan-like syndrome with loose anagen hair-1

Noonan syndrome (NS), the most common of the RASopathies, is a developmental disorder caused by heterozygous germline mutations in genes encoding proteins in the RAS-MAPK signaling pathway. Noonan-like syndrome with loose anagen hair (NSLH, including NSLH1, OMIM #607721 and NSLH2, OMIM #617506) is characterized by typical features of NS with additional findings of macrocephaly, loose anagen hair, growth hormone deficiency in some, and a higher incidence of intellectual disability. All NSLH1 reported cases to date have had an SHOC2 c.4A>G, p.Ser2Gly mutation; NSLH2 cases have been reported with a PPP1CB c.146G>C, p.Pro49Arg mutation, or c.166G>C, p.Ala56Pro mutation. True cleft palate does not appear to have been previously reported in individuals with NS or with NSLH. While some patients with NS have had growth hormone deficiency (GHD), other endocrine abnormalities are only rarely documented. We present a female patient with NSLH1 who was born with a posterior cleft palate, micrognathia, and mild hypotonia. Other findings in her childhood and young adulthood years include hearing loss, strabismus, and hypopituitarism with growth hormone, thyroid stimulating hormone (TSH), and gonadotropin deficiencies. The SHOC2 mutation may be responsible for this patient's additional features of cleft palate and hypopituitarism.

Low-loss arrayed waveguide grating at 760 nm

An arrayed waveguide grating (AWG) at 760 nm is demonstrated with an insertion loss smaller than 0.5 dB. Interface roughness and waveguide length errors contribute much more to scattering loss and phase errors at 760 nm than at longer wavelengths, thus requiring improved design and fabrication. This Letter details how this is achieved by minimizing interfacial scattering, grating side-order excitation, and phase errors in the AWG. With silicon nitride core and silicon dioxide clad waveguides on silicon, this AWG is compatible with heterogeneously integrated lasers for on-chip spectral beam combining.

T Follicular Helper Cell-Dependent Clearance of a Persistent Virus Infection Requires T Cell Expression of the Histone Demethylase UTX

Epigenetic changes, including histone methylation, control T cell differentiation and memory formation, though the enzymes that mediate these processes are not clear. We show that UTX, a histone H3 lysine 27 (H3K27) demethylase, supports T follicular helper (Tfh) cell responses that are essential for B cell antibody generation and the resolution of chronic viral infections. Mice with a T cell-specific UTX deletion had fewer Tfh cells, reduced germinal center responses, lacked virus-specific immunoglobulin G (IgG), and were unable to resolve chronic lymphocytic choriomeningitis virus infections. UTX-deficient T cells showed decreased expression of interleukin-6 receptor-α and other Tfh cell-related genes that were associated with increased H3K27 methylation. Additionally, Turner Syndrome subjects, who are predisposed to chronic ear infections, had reduced UTX expression in immune cells and decreased circulating CD4(+) CXCR5(+) T cell frequency. Thus, we identify a critical link between UTX in T cells and immunity to infection.

Fully integrated hybrid silicon two dimensional beam scanner

In this work we present the first fully-integrated free-space beam-steering chip using the hybrid silicon platform. The photonic integrated circuit (PIC) consists of 164 optical components including lasers, amplifiers, photodiodes, phase tuners, grating couplers, splitters, and a photonic crystal lens. The PIC exhibited steering over 23° x 3.6° with beam widths of 1° x 0.6°.

Heterogeneously integrated III-V-on-silicon multibandgap superluminescent light-emitting diode with 290 nm optical bandwidth

A broadband superluminescent III-V-on-silicon light-emitting diode (LED) was realized. To achieve the large bandwidth, quantum well intermixing and multiple die bonding of InP on a silicon photonic waveguide circuit were combined for the first time, to the best of our knowledge. The device consists of four sections with different bandgaps, centered around 1300, 1380, 1460, and 1540 nm. The fabricated LEDs were connected on-chip in a serial way, where the light generated in the smaller bandgap sections travels through the larger bandgap sections. By balancing the pump current in the four LEDs, we achieved 292 nm of 3 dB bandwidth and an on-chip power of -8  dBm.

Hybrid III/V silicon photonic source with integrated 1D free-space beam steering

A chip-scale optical source with integrated beam steering is demonstrated. The chip was fabricated using the hybrid silicon platform and incorporates an on-chip laser, waveguide splitter, amplifiers, phase modulators, and surface gratings to comprise an optical phased array with beam steering across a 12° field of view in one axis. Tuning of the phased array is used to achieve 1.8°(steered axis)×0.6°(nonsteered axis) beam width with 7 dB background suppression for arbitrary beam direction within the field of view.

Growth hormone therapy in Turner syndrome

Short stature is the single most common physical abnormality in Turner syndrome (TS) with adult stature averaging 20 cm shorter than that of the general population. Randomized, placebo-controlled studies to final adult height have proven that GH therapy is effective in increasing stature in TS. Recently, randomized, controlled studies have demonstrated that adjunctive therapies with low-dose estrogen or low-dose oxandrolone enhance stature further. These therapies may provide benefits beyond height augmentation.

Growth hormone treatment does not affect incidences of middle ear disease or hearing loss in infants and toddlers with Turner syndrome

CONTEXT

No randomized, controlled, prospective study has evaluated the effect of growth hormone (GH) on the rates of middle ear (ME) disease and hearing loss in girls with Turner syndrome (TS).

DESIGN

A 2-year, prospective, randomized, controlled, open-label, multicenter, clinical trial ('Toddler Turner Study'; August 1999 to August 2003) was carried out.

SETTING

The study was conducted at 11 US pediatric endocrine centers.

SUBJECTS

Eighty-eight girls with TS, aged 9 months to 4 years, were enrolled.

INTERVENTION

The interventions comprised recombinant GH (50 microg/kg/day, n = 45) or no treatment (n = 43) for 2 years.

MAIN OUTCOME MEASURES

The outcome measures included occurrence rates of ear-related problems, otitis media (OM) and associated antibiotic treatments, tympanometric assessment of ME function and hearing assessment by audiology.

RESULTS

At baseline, 57% of the girls (mean age = 1.98 +/- 1.00 years) had a history of recurrent OM, 33% had undergone tympanostomy tube (t-tube) insertion and 27% had abnormal hearing. There was no significant difference between the treatment groups for annual incidence of OM episodes (untreated control: 1.9 +/- 1.4; GH-treated: 1.5 +/- 1.6, p = 0.17). A quarter of the subjects underwent ear surgeries (mainly t-tube insertions) during the study. Recurrent or persistent abnormality of ME function on tympanometry was present in 28-45% of the girls without t-tubes at the 6 postbaseline visits. Hearing deficits were found in 19-32% of the girls at the annual postbaseline visits. Most of these were conductive deficits, however, 2 girls had findings consistent with sensorineural hearing loss, which was evident before 3 years of age.

CONCLUSIONS

Ear and hearing problems are common in infants and toddlers with TS and are not significantly influenced by GH treatment. Girls with TS need early, regular and thorough ME monitoring by their primary care provider and/or otolaryngologist, and at least annual hearing evaluations by a pediatric audiologist.

Approach to the patient with Turner syndrome

Turner syndrome (TS) occurs in about 1:4000 live births and describes females with a broad constellation of problems associated with loss of an entire sex chromosome or a portion of the X chromosome containing the tip of its short arm. TS is associated with an astounding array of potential abnormalities, most of them thought to be caused by haploinsufficiency of genes that are normally expressed by both X chromosomes. A health care checklist is provided that suggests screening tests at specific ages and intervals for problems such as strabismus, hearing loss, and autoimmune thyroid disease. Four areas of major concern in TS are discussed: growth failure, cardiovascular disease, gonadal failure, and learning disabilities. GH therapy should generally begin as soon as growth failure occurs, allowing for rapid normalization of height. Cardiac imaging, preferably magnetic resonance imaging, should be performed at diagnosis and repeated at 5- to 10-yr intervals to assess for congenital heart abnormalities and the emergence of aortic dilatation, a precursor to aortic dissection. Hypertension should be aggressively treated. For those with gonadal dysgenesis, hormonal replacement therapy should begin at a normal pubertal age and be continued until the age of 50 yr. Transdermal estradiol provides the most physiological replacement. Finally, nonverbal learning disabilities marked by deficits in visual-spatial-organizational skills, complex psychomotor skills, and social skills are common in TS. Neuropsychological testing should be routine and families given support in obtaining appropriate therapy, including special accommodations at school.

Moving toward an understanding of hormone replacement therapy in adolescent girls: looking through the lens of Turner syndrome

Turner syndrome (TS) is a relatively common disorder of phenotypic females caused by loss of all or part of the second sex chromosome. Most individuals with TS have short stature and gonadal dysgenesis and are at risk for many other medical and learning problems. In the 45,X ovary, germs cells multiply quite normally during fetal development, but there is accelerated atresia of oocytes in the second half of pregnancy that produces gonadal insufficiency by birth. In girls with other karyotypes, especially those mosaic for 45,X/46,XX, gonadal function may be normal or near-normal. In this chapter, management goals for gonadal insufficiency in girls with TS are presented. The effects of estrogen deficiency and its replacement on three specific problems associated with TS-short stature, cardiovascular disease, and developmental differences in brain structure and function-are explored. General guidelines for estrogen replacement therapy using transdermal estrogen, the most physiologic option, are provided and future research goals are outlined.

Growth hormone treatment of early growth failure in toddlers with Turner syndrome: a randomized, controlled, multicenter trial

CONTEXT

Typically, growth failure in Turner syndrome (TS) begins prenatally, and height sd score (SDS) declines progressively from birth.

OBJECTIVE

This study aimed to determine whether GH treatment initiated before 4 yr of age in girls with TS could prevent subsequent growth failure. Secondary objectives were to identify factors associated with treatment response, to determine whether outcome could be predicted by a regression model using these factors, and to assess the safety of GH treatment in this young cohort.

DESIGN

This study was a prospective, randomized, controlled, open-label, multicenter clinical trial (Toddler Turner Study, August 1999 to August 2003).

SETTING

The study was conducted at 11 U.S. pediatric endocrine centers.

SUBJECTS

Eighty-eight girls with TS, aged 9 months to 4 yr, were enrolled.

INTERVENTIONS

Interventions comprised recombinant GH (50 mug/kg.d; n = 45) or no treatment (n = 43) for 2 yr.

MAIN OUTCOME MEASURE

The main outcome measure was baseline-to-2-yr change in height SDS.

RESULTS

Short stature was evident at baseline (mean length/height SDS = -1.6 +/- 1.0 at mean age 24.0 +/- 12.1 months). Mean height SDS increased in the GH group from -1.4 +/- 1.0 to -0.3 +/- 1.1 (1.1 SDS gain), whereas it decreased in the control group from -1.8 +/- 1.1 to -2.2 +/- 1.2 (0.5 SDS decline), resulting in a 2-yr between-group difference of 1.6 +/- 0.6 SDS (P < 0.0001). The baseline variable that correlated most strongly with 2-yr height gain was the difference between mid-parental height SDS and subjects' height SDS (r = 0.32; P = 0.04). Although attained height SDS at 2 yr could be predicted with good accuracy using baseline variables alone (R(2) = 0.81; P < 0.0001), prediction of 2-yr change in height SDS required inclusion of initial treatment response data (4-month or 1-yr height velocity) in the model (R(2) = 0.54; P < 0.0001). No new or unexpected safety signals associated with GH treatment were detected.

CONCLUSION

Early GH treatment can correct growth failure and normalize height in infants and toddlers with TS.

Differences in follicle-stimulating hormone secretion between 45,X monosomy Turner syndrome and 45,X/46,XX mosaicism are evident at an early age

CONTEXT

Little information exists regarding FSH values in very young girls with Turner syndrome (TS).

OBJECTIVES

The objective of the study was to evaluate the pattern, natural progression, and karyotype-related differences in FSH secretion in young, prepubertal girls with TS.

STUDY DESIGN

FSH was measured at study entry and annually for 2 yr.

SETTING

The Toddler Turner study was conducted at 11 U.S. pediatric endocrine centers.

STUDY PARTICIPANTS

Eighty-eight girls with karyotype-proven TS aged 9 months to 4 yr participated in the study.

MAIN OUTCOME MEASURES

By-karyotype differences in FSH concentration and age-related changes in FSH were measured.

RESULTS

Mean (+/- SD) FSH was markedly elevated in the 45,X (n = 56: 68.3 +/- 36.0 IU/liter) and Other groups [n = 15 (excluding three subjects with Y-containing karyotypes): 52.7 +/- 50.8 IU/liter] but was minimally elevated in girls with 45,X/46,XX mosaicism (n = 14: 10.1 +/- 13.5 IU/liter, P < 0.005 both comparisons). Over the 2-yr period, FSH declined in the 45,X group (-13.4 IU/liter.yr, P < 0.0001). Nonetheless, only three of 159 FSH values fell within normal range for age at any time during the 2-yr study. FSH decline was similar in the Other group (-14.3 IU/liter.yr, P = 0.0032). In contrast, no significant decrease in FSH with age was observed in the 45,X/46,XX group.

CONCLUSIONS

In contrast to the original report of FSH concentrations in individuals with TS, this study demonstrates distinct differences in patterns of FSH secretion between young girls with monosomy TS, who have persistent elevation of FSH to age 6 yr, and those with 45,X/46,XX mosaicism, whose FSH values suggest retained ovarian function in the majority. These findings have implications for patient management and family counseling.

Evidence for early initiation of growth hormone and transdermal estradiol therapies in girls with Turner syndrome

Results from the first randomized, controlled trial of growth hormone (GH) therapy in girls with Turner syndrome (TS) followed to final height firmly establish that GH increases final adult stature. It is widely believed that the efficacy of GH is dependent upon the duration of therapy and dosing (longer duration and higher dose give taller final height). In a recent observational study involving more than 1500 French girls with TS, multivariate analyses demonstrated that the age at initiation of GH therapy accounted for a large percentage of the variance (44%) in response. Age at initiation of estrogen therapy was the second most important factor in determining GH effect (later initiation, taller final height), accounting for 22% of the variance. Overall, 0.3 cm in adult height was gained for every year that estrogen therapy was delayed. However, analyses of the French data restricted to patients with induced puberty revealed that those treated with percutaneous estradiol attained a height 2.1cm taller than those using oral estradiol or other estrogen preparations. In another study, girls receiving GH therapy (n=14) who were randomized to receive intramuscular (IM) depot estradiol early (12.0-12.9 years) attained at least as much height as those who initiated it late (14.0-14.9 years). These results are consistent with the observations in adult women that oral estrogens decrease IGF-I serum levels and suppress the IGF-independent metabolic effects of GH, while transdermal estrogens do not. Taken together, these studies suggest that girls with TS should begin GH therapy as soon as growth failure is demonstrated and that puberty should be induced with transdermal or IM estradiol. Girls for whom height is normalized with GH therapy in early childhood have the opportunity to undergo puberty at an age-appropriate time and still achieve a normal adult stature.

Continuous subcutaneous glucose monitoring in children with type 1 diabetes mellitus: a single-blind, randomized, controlled trial

BACKGROUND

Tight glycemic control delays the long-term complications of type 1 diabetes mellitus (T1DM) but increases the risk for hypoglycemia. The continuous glucose-monitoring system (CGMS) provides blood glucose (BG) readings every 5 min, and its accuracy and reliability has been established in adults. However, there are limited data on its efficacy and safety in children. The purpose of this study was to determine if CGMS use improves metabolic control in children with T1DM.

METHODS

Twenty-seven children (12 male) with T1DM participated in this single-blind, randomized, controlled trial. Participants (age: 11.4 +/- 3.7 (mean +/- SD) yr, range: 7-17 yr) were randomized to an intervention group (n = 18) or a control group (n = 9). Both groups wore the CGMS for 72-h periods at 0, 2, and 4 months. Adjustments in therapy for the intervention group were based on both CGMS and self-monitoring of BG (SMBG) data, while only SMBG data were used for the control group. Hemoglobin A1c (HbA1c) was determined at 0, 2, 4, and 6 months. The change in HbA1c from 0 to 6 months (HbA1c(Delta1-4)) and mean daily area under the CGMS curve for glucose <70 mg/dL area under the curve (AUC(<70)) were compared between groups.

RESULTS

At study entry, HbA1c levels were similar in the intervention and control groups (8.4 +/- 0.98 and 8.8 +/- 0.86%, respectively; p = 0.12) but were significantly lower in the intervention group compared with the control group at study completion (7.8 +/- 0.88 and 8.6 +/- 0.95%, respectively; p = 0.02). The decrease in HbA1c of 0.61 +/- 0.68% in the intervention group was statistically significant (p = 0.03), whereas the decrease in HbA1c of 0.28 +/- 0.78% in the control group was not. Nonetheless, the differences in HbA1c(Delta1-4) between groups did not reach statistical significance (p = 0.13). There was no statistically significant difference in AUC(<70) between study groups (p = 0.18).

CONCLUSION

CGMS use may improve metabolic control in children with T1DM without increasing the risk for hypoglycemia.

Gonadotropin secretion in girls with turner syndrome measured by an ultrasensitive immunochemiluminometric assay

BACKGROUND/AIM

Gonadotropin levels measured by radioimmunoassays are high in girls with Turner syndrome (TS), but overlap significantly with those of normal girls. We hypothesized that gonadotropin levels would be above the normal range in TS when measured by ultrasensitive assays.

METHODS

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were measured in 68 TS, and 133 control girls using ultrasensitive immunochemiluminometric assays (ICMA).

RESULTS

FSH levels in TS and normal girls were highest in early childhood (56.0 +/- 39.7 and 2.3 +/- 1.8 IU/l, respectively), declined at 6-10 years of age (11.3 +/- 13.1 and 1.8 +/- 0.9 IU/l, respectively), and then increased again (104.4 +/- 68.9 and 4.9 +/- 2.4 IU/l, respectively). FSH was in the normal range on 11 of 27 occasions in TS girls with ages 5-10 years, and on 3 of 44 occasions in >10 years. Although average LH values were higher than those of controls, they often overlapped the normal range.

CONCLUSION

A significant number of TS girls have normal gonadotropins by ICMA. Spontaneous gonadotropin levels are not an adequate screening test for the diagnosis of TS but may prove useful for predicting the gonadal function and determining the appropriate timing of estrogen replacement therapy.

Visuospatial executive function in Turner syndrome: functional MRI and neurocognitive findings

Turner syndrome is a genetic disorder that results from an abnormal or missing X chromosome in females and is typically associated with impairments in visuospatial, but not verbal, information processing. These visuospatial processing impairments may be exacerbated with increased task demands, such as those engaged during working memory (WM). While previous studies have examined spatial WM function in Turner syndrome, none have directly compared the neural correlates of spatial and verbal WM processes across the encoding, maintenance and retrieval phases. We employed both neurocognitive assessments and functional MRI (fMRI) to examine the neural circuitry underlying both verbal and visuospatial WM functions in individuals with Turner syndrome and normal controls. We furthermore examined the vulnerability of task-related fMRI activation to distracters presented during WM maintenance. Fifteen healthy female volunteers and eight individuals with Turner syndrome performed a delayed-response WM task during fMRI scanning. Neurocognitive tests revealed impaired performance across both verbal and spatial domains in Turner syndrome, with greater impairment on tasks with WM demands. Frontoparietal regions in controls showed significantly sustained levels of activation during visuospatial WM. This sustained activation was significantly reduced in the group with Turner syndrome. Domain-specific activation of temporal regions, in contrast, did not differ between the two groups. Sensory distraction during the WM maintenance phase did not differentially alter frontoparietal activation between the two groups. The results reveal impaired frontoparietal circuitry recruitment during visuospatial executive processing in Turner syndrome, suggesting a significant role for the X chromosome in the development of these pathways.

Central Obesity, the Metabolic Syndrome, and Plasminogen Activator Inhibitor-1 in Young Adults

PURPOSE

To determine the association of central obesity with the components of the metabolic syndrome (i.e., hyperinsulinemia, hypertension, hypertriglyceridemia, low levels of high-density lipoprotein cholesterol [HDL-C]) and plasma levels of plasminogen activator inhibitor-1 (PAI-1) in young adults. We hypothesized that central obesity as determined by waist circumference would be predictive of components of the metabolic syndrome and of PAI-1.

DATA SOURCES

Participants in this descriptive study consisted of 85 healthy young adults aged 19-22 years, 62% women who fasted for 12 h prior to data collection in the General Clinical Research Center at a major university hospital medical center in the southeastern United States.

CONCLUSIONS

The majority of the participants had one or more components of the metabolic syndrome (n= 43, 51%). Central obesity was present in 14.1% and was more common in women than men (chi(2)= 5.11; p= 0.021). Central obesity was significantly and positively correlated with elevated blood pressure (BP) and levels of insulin and PAI-1 while being negatively correlated with HDL-C. In multiple regression analyses, diastolic BP, insulin, and HDL-C were predictors of waist circumference (R(2)= 0.615). In a separate multiple regression, PAI-1 was predicted by waist circumference (R(2)= 0.331).

IMPLICATIONS FOR PRACTICE

Many otherwise healthy young adults have one or more components of the metabolic syndrome. Assessment and institution of preventative measures for obesity and the components of the metabolic syndrome should begin in childhood. Furthermore, determination of waist circumference especially in young women may aid the practitioner to identify those at risk for the metabolic syndrome earlier in their disease trajectory. Furthermore, insulin resistance is believed to occur initially in the trajectory of the metabolic syndrome, making it a principal contender for suitable interventions to reduce risk for both type 2 diabetes and cardiovascular disease (CVD). Homeostatic model assessment for insulin resistance was used to assess for insulin resistance among the euglycemic participants. Recording the presence of insulin resistance will aid the practitioner in determining if a low-risk patient is in peril for development of type 2 diabetes and/or CVD. Early cardiovascular risk recognition is vital to clinical practice as it allows more time for the practitioner to counsel patients for the essential planning needed to make lifestyle changes.

Ascertainment bias in Turner syndrome: new insights from girls who were diagnosed incidentally in prenatal life

OBJECTIVE

To evaluate differences in phenotype and other clinical features between patients who have Turner syndrome diagnosed incidentally (on the basis of a prenatal karyotype performed for reasons unrelated to suspicion of Turner syndrome, eg, advanced maternal age) or traditionally (on the basis of either a prenatal karyotype performed for abnormal ultrasound findings or a postnatal karyotype performed for clinical findings suggesting Turner syndrome).

METHODS

Analysis was performed on baseline data from 88 girls, aged 9 months to 4 years, who were randomized into a multicenter growth hormone intervention trial. Baseline information included a detailed medical history (especially of cardiac and renal anomalies), examination for presence of phenotypic features characteristic of Turner syndrome, length or height (depending on age) expressed as a standard deviation score, and weight standard deviation score. Patients were classified to either the "incidental" (N = 16) or the "traditional" (N = 72) diagnosis group as described above.

RESULTS

The incidental group had significantly fewer total phenotypic features of Turner syndrome than the traditional group (3.6 +/- 2.9 vs 6.7 +/- 2.9). When subgrouped by karyotype, the proportion of patients who manifested phenotypic features was greatest in patients with a 45,X nonmosaic karyotype, lowest in the patients with 45,X/46,XX mosaicism, and intermediate in those with "other" karyotypes. Fewer congenital cardiac defects were observed in the incidental group (31%) compared with the traditional group (64%), but there was no difference between the groups in the prevalence of renal defects. Karyotype distribution differed significantly between the traditional and incidental groups: 74% versus 19% had the nonmosaic 45,X karyotype in the traditional group and 7% versus 56% had the mosaic 45,X/46,XX karyotype.

CONCLUSIONS

Patients whose Turner syndrome was diagnosed incidentally had significantly fewer phenotypic features and cardiac defects, as well as a greater proportion of mosaic karyotypes, compared with patients whose Turner syndrome was diagnosed clinically. These results support the theory that significant ascertainment bias exists in our understanding Turner syndrome, with important implications for prenatal counseling.

Health supervision for children with Turner syndrome

This report is designed to assist the pediatrician in caring for the child in whom the diagnosis of Turner syndrome has been confirmed by karyotyping. The report is meant to serve as a supplement to the American Academy of Pediatrics' "Recommendations for Preventive Pediatric Care" and emphasizes the importance of continuity of care and the need to avoid its fragmentation by ensuring a medical home for every girl with Turner syndrome. The pediatrician's first contact with a child with Turner syndrome may occur during infancy or childhood. This report also discusses interactions with expectant parents who have been given the prenatal diagnosis of Turner syndrome and have been referred for advice.

Kyphosis in a Turner syndrome population

OBJECTIVE

The purpose of this study was to determine the prevalence of kyphosis in a Turner syndrome (TS) population.

METHODS

Standing lateral thoracic spine and standing anterior-posterior (A-P) scoliosis radiographs were obtained on all girls with TS between the ages of 5 and 18 years seen in a TS clinic between July 2000 and March 2001. Medical histories were reviewed, and a pediatric orthopedic surgeon evaluated the radiographs of each patient (N = 25). Excessive kyphosis was defined as an A-P curvature >40 degrees, vertebral wedging as any A-P deformity >5 degrees at an individual vertebral body, and scoliosis as a lateral curvature >10 degrees.

RESULTS

Fifteen (60%) of 25 patients were found to have abnormal radiographic findings: 10 (40%) of 25 with excessive kyphosis, 10 (40%) of 25 with vertebral wedging, and 5 (20%) of 25 with scoliosis. Forty-eight percent of the girls had both excessive kyphosis and/or vertebral body wedging. Two girls had kyphosis > or =55 degrees, and 5 had scoliosis > or =25 degrees. Girls with excessive kyphosis and/or vertebral body wedging were older (13.6 +/- 3.9 years vs 10.6 +/- 2.8 years).

CONCLUSIONS

The prevalence of excessive kyphosis and vertebral body wedging seems to be increased in girls with TS and corresponds with advancing age. Routine radiologic surveillance may facilitate detection of developing deformities so that treatment with a brace can be considered to prevent or slow the process.

The effect of growth hormone on craniofacial growth and dental maturation in Turner syndrome

Serial cephalometric and panoramic radiographs from a mixed longitudinal group of 28 subjects with Turner syndrome (TS), age 4.4-19.0 years, were evaluated for annualized growth increments of the craniofacial complex and dental development and were compared with a longitudinal control group from the Burlington growth study. The short and retrognathic face characteristic of the syndrome was due largely to the increased cranial base angle, decreased posterior face height, and decreased mandibular length, all of which were significantly different from the controls. Although increases in statural height occurred in the TS children who were treated with human growth hormone (GH), there was little or no effect on growth of the jaws, particularly in the older subjects, and the characteristic facies of the syndrome persisted. Dental development was advanced in all TS subjects, and GH administration had no effect on the rate of dental development.

Delayed diagnoses of Turner's syndrome: proposed guidelines for change

OBJECTIVE

To measure the delays in diagnosis of Turner's syndrome (TS) and to propose strategies for earlier screening and diagnosis.

METHODS

The medical records of 81 girls with TS were reviewed for age at diagnosis, reason(s) for karyotype analysis, and clinical features including growth failure. Delay in diagnosis was calculated as equal to age at diagnosis for children born with lymphedema and/or 2 or more of the following dysmorphic features: webbed neck, nail dysplasia, high palate, and short fourth metacarpal. For all others, delay in diagnosis was calculated as the difference between the age at which height fell below the 5th percentile and the age at which the diagnosis of TS was made.

RESULTS

Lymphedema was the key to diagnosis in 97% of the girls diagnosed with TS in infancy, and short stature was the key to diagnosis for 82% of the girls diagnosed in childhood or adolescence. For girls diagnosed in childhood or adolescence, the delay in diagnosis averaged 7.7 +/- 5.4 years. Many had dysmorphic features and/or a history of lymphedema at birth, and diagnosis was made an average of 5.3 years after patients had fallen below the 5th percentile for height. By the time of diagnosis, patients were very short, averaging -2.9 SD in height.

CONCLUSIONS

The diagnosis of TS is often delayed. We recommend karyotype analysis for all girls with unexplained short stature, delayed puberty, webbed neck, lymphedema, or coarctation of the aorta. Furthermore, karyotype analysis should be strongly considered for those who remain above the 5th percentile for height but have 2 or more features of TS, including high palate, nail dysplasia, short fourth metacarpal, and strabismus.

Early-onset sensorineural hearing loss in a child with Turner syndrome

Turner syndrome is among the more common but less familiar syndromes that include sensorineural hearing loss and middle ear disease. This article provides a review of the syndrome, an illustrative case, and a review of specific issues relevant to audiologic management of patients with Turner syndrome.

Early-Onset Sensorineural Hearing Loss in a Child with Turner Syndrome

Turner syndrome is among the more common but less familiar syndromes that include sensorineural hearing loss and middle ear disease. This article provides a review of the syndrome, an illustrative case, and a review of specific issues relevant to audiologic management of patients with Turner syndrome.

Abbreviations: GH = growth hormone, TS = Turner syndrome

Nutritional rickets in African American breast-fed infants

OBJECTIVE

To analyze the characteristics of infants and children diagnosed with nutritional rickets at two medical centers in North Carolina in the 1990s.

STUDY DESIGN

The physical and radiographic findings, calcium, phosphorus, alkaline phosphatase, and 25-hydroxyvitamin D levels of infants and children diagnosed with nutritional rickets at two medical centers were reviewed. Breast-feeding data were obtained from the North Carolina Women, Infants and Children Program (WIC).

RESULTS

Thirty patients with nutritional rickets were first seen between 1990 and June of 1999. Over half of the cases occurred in 1998 and the first half of 1999. All patients were African American children who were breast fed without receiving supplemental vitamin D. The average duration of breast-feeding was 12.5 months. The age at diagnosis was 5 to 25 months, with a median age of 15.5 months. Growth failure was common: length was <5th percentile in 65% of cases, and weight was <5th percentile in 43%.

CONCLUSION

Factors that may have contributed to the increase in referrals of children with nutritional rickets include more African American women breast-feeding, fewer infants receiving vitamin D supplements, and mothers and children exposed to less sunlight. We recommend that all dark-skinned breast-fed infants and children receive vitamin D supplementation.

Turner syndrome: a pattern of early growth failure

The purpose of this study was to determine the pattern of early growth in girls with Turner syndrome. Analysis was performed on a total of 464 longitudinal measurements of height, obtained from birth to 8 years of age from 37 girls with Turner syndrome who did not have significant cardiac disease or autosomal abnormalities. All data were obtained prior to the initiation of any hormonal therapy. Mean height SDS fell from -0.5 at birth to -1.5 at age 1 year and -1.8 at age 1.5 years. Growth curves fitted using the first two components of the infancy-childhood-puberty model of growth revealed that growth failure was due to (a) mild growth retardation in utero, (b) slow growth during infancy, (c) delayed onset of the childhood component of growth and (d) slow growth during childhood. Physicians should consider the diagnosis of Turner syndrome in any girl with an unexplained failure to thrive or with short stature, even during the first 2 years of life.

Mouse mutants lacking the type 2 IGF receptor (IGF2R) are rescued from perinatal lethality in Igf2 and Igf1r null backgrounds

The cation-dependent and cation-independent mannose 6-phosphate receptors (CD- and CI-MPRs) bind the phosphomannosyl recognition marker of lysosomal hydrolases, but in mammals the latter also interacts with insulin-like growth factor II (IGF-II). While IGF signaling is mediated by the type 1 IGF receptor (IGF1R), the type 2 receptor (IGF2R/CI-MPR) serves IGF-II turnover. Mouse mutants inheriting maternally a targeted disruption of the imprinted Igf2r gene, which is normally expressed only from the maternal allele, have increased serum and tissue levels of IGF-II and exhibit overgrowth (135% of normal birthweight) and generalized organomegaly, kinky tail, postaxial polydactyly, heart abnormalities, and edema. These mutants usually die perinatally, but a small minority can survive depending on genetic background and can occasionally reproduce, except for some females characterized by an imperforate vagina and hydrometrocolpos. Consistent with the hypothesis that lethality in the absence of IGF2R-mediated turnover is caused by excess of IGF-II overstimulating IGF1R, Igf2r mutants are completely rescued when they carry a second mutation eliminating either IGF-II or IGF1R. Normal embryonic development of the Igf1r/Igf2r double mutants, which differ from wild-type siblings only in the pattern of postnatal growth, appears to occur by signaling of IGF-II, being in excess, through a genetically identified unknown receptor, since triple mutants lacking IGF1R, IGF2R, and IGF-II are nonviable dwarfs (30% of normal size). In contrast with the Igf2r/Igf2 double mutants, mice lacking IGF2R/CI-MPR and CD-MPR survive in an IGF-II null background at a very low frequency and only for a few postnatal weeks, indicating that the mannose 6-phosphate-mediated lysosomal enzyme trafficking is essential for viability.

Preoperative evaluation of intersex patients with pelvic magnetic resonance imaging in search of Y chromosome-bearing gonadal tissue

OBJECTIVE

To illustrate the utility of preoperative magnetic resonance imaging in the evaluation of intersex patients who require gonadectomy.

DESIGN

Case reports of two phenotypic females having karyotypes containing a Y chromosome whose preoperative evaluation included pelvic magnetic resonance imaging.

SETTING

Tertiary academic referral center.

MAIN OUTCOME MEASURE

Pelvic magnetic resonance imaging for gonadal localization.

RESULTS

Preoperative evaluation with magnetic resonance imaging correctly identified the most appropriate surgical approach to gonadectomy.

CONCLUSIONS

Pelvic magnetic resonance imaging can be useful in the preoperative evaluation of intersex patients having nonpalpable Y chromosome-bearing gonadal tissue.

Nutritional insult and recovery in the neonatal rat cerebellum: insulin-like growth factors (IGFs) and their binding proteins (IGFBPs)

Alterations in growth caused by neonatal malnutrition may be mediated in part by changes in insulin-like growth factor (IGF) and IGF binding protein (IGFBP) expression. Since the neonatal rat cerebellum undergoes a transient, proliferative growth phase in the first two weeks of life, this structure was used to determine whether alterations in circulating and tissue IGFs and IGFBPs may mediate effects of impaired nutrition on the developing central nervous system. Gravid rats were placed on a 4% (protein-calorie deprived, D) or 20% (control, C) protein diets one day prior to delivery and allowed to nurse their pups postpartum. Pups nursing from D mothers received a limited volume of milk and were calorically deprived. Some litters of D pups were foster fed by C mothers from day 8 to day 13 to constitute a recovery group (R). Cerebellar weight, protein, and DNA content in D pups were less than C, p < 0.001. In R pups, DNA and protein returned to C levels by day 13. Between days 6 and 13, serum IGF-I levels rose from 158 +/- 18 to 210 +/- 18 ng/ml in C but remained low in D (47 +/- 6 ng/ml and 25 +/- 3 ng/ml), respectively. In R pups, serum IGF-I partially recovered during this time, and increased from 49 +/- 5 to 110 +/- 7 ng/ml. In cerebellar extracts, IGF-I levels in both C and D were lower at 13 days than at 6 days, p < 0.05 and p < 0.005, respectively. IGF-I levels in C were similar at day 9 and day 11 and were consistently higher than D (11.84 +/- 0.83 vs 8.56 +/- 0.92 ng/g, p < 0.02 C vs D). In R, IGF-I was reduced on day 11, but was similar to C on day 13. Serum IGF-II in D was lower than C, p < 0.01, and did not increase in the R group. Cerebellar IGF-II was virtually undetectable in either group. Immunoprecipitation and ligand blotting studies of serum demonstrated that circulating levels of 32-34 K IGFBPs were increased 3-4 fold in D vs C, reflecting high levels of IGFBP-1 and/or -2, while levels of 24 K IGFBP-4 were lower in D vs C. By contrast, immunoprecipitation and ligand blotting of cerebellar extracts detected IGFBP-2 and -4, but did not detect IGFBP-1. Further, tissue levels of IGFBP-2 were not increased in D vs C, and levels of IGFBP-4 also were not markedly affected by nutritional deprivation. These results suggest that alterations in tissue content and the availability of IGF-I only modestly contributed to the effects of impaired nutrition in the developing central nervous system.

Effect of intravenous insulin-like growth factor I in two patients with leprechaunism

Leprechaunism (Donohue syndrome) is an autosomal recessive disorder characterized by hyperglycemia, extreme insulin resistance, dysmorphic features, failure to thrive, and early death. In this study, recombinant IGF-I, which has both insulin-like and anabolic effects, was administered to two infants with leprechaunism in an attempt to reduce hyperglycemia and improve nutritional status. IGF-I was infused for 66 h in patient FL-1 and 62 h in patient NC-2, with maximal infusion rates of 110 and 40 micrograms/kg/h, respectively. Although supraphysiologic concentrations of IGF-I were achieved (459 and 1583 micrograms/L in FL-1 and NC-2, respectively), there were no apparent glucose-lowering or nitrogen-sparing effects. Insulin concentrations decreased from extremely high values (16804 and 10224 pmol/L) but remained elevated (611 pmol/L in FL-1 and 5869 pmol/L in NC-2). No changes in serum and urinary urea nitrogen or electrolytes occurred. IGF binding protein-2, which was the predominant IGF binding protein in serum by ligand blot and immunoblot, did not change with IGF-I infusion. IGF binding protein-3 levels were low at baseline and increased slightly during the infusion. We hypothesize that the lack of significant glucose-lowering and anabolic responses to IGF-I could be secondary to a postreceptor defect in IGF-I signaling resulting from the absence of functional insulin receptors.

The effect of dietary protein supplementation on insulin-like growth factors (IGFs) and IGF-binding proteins in children with shigellosis

Nutrient deficiency causes growth failure and decreases serum insulin-like growth factor-I (IGF-I) concentrations. Because IGFBPs modulate the concentrations and availability of IGFs in serum, IGF-binding proteins (IGFBPs) were measured along with IGF-I and IGF-II before and after 21 days of refeeding in 22 undernourished Bangladeshi children (2-4 yr of age) with shigellosis. The effects of a 150 Cal/kg.day diet with a normal protein (6%; n = 10) or high protein (15%; n = 12) content were studied. The results were compared with those of 25 age-matched healthy American children (controls). Body weight gain was better in patients receiving the high protein diet than in those receiving the normal protein diet. In both groups, initial IGF-I (32 +/- 6 and 24 +/- 7 ng/mL; mean +/- SD) and IGF-II (177 +/- 15, 174 +/- 45 ng/mL) concentrations were low compared to controls (100 +/- 12 and 542 +/- 29 ng/mL, respectively; P < 0.007). After refeeding, IGF-I increased to 160 +/- 26 ng/mL on the normal protein diet and to 322 +/- 41 ng/mL on the high protein diet, exceeding values in controls (P < 0.007). IGF-II increased more than 2-fold on each diet (P < 0.007), reaching control values. IGFBP-2 concentrations before refeeding were twice those in controls (750 +/- 200 vs. 317 +/- 33 ng/mL; P < 0.007) and normalized after refeeding in the high protein group (288 +/- 32 ng/mL; P = NS), but remained elevated in the normal protein group (526 +/- 77 ng/mL; P < 0.007). IGFBP-3 levels before refeeding were low and returned to normal on each diet. IGFBP-3 proteolytic activity in serum was initially increased and declined on the high protein diet. In conclusion, protein content in the refeeding diet differentially affects IGFs and IGFBPs in young undernourished children with infection. IGF-I and IGFBP-2 seem to be particularly sensitive to dietary protein alterations. We speculate that an increase in IGF-I concentrations, normalization of IGFBP levels, and a decrease in IGFBP-3 proteolytic activity in serum may all be involved in the improved recovery and catch-up growth observed with the high protein diet.

Homozygous deletion of the human insulin receptor gene results in leprechaunism

Homozygous inactivation of a gene, as is frequently performed to generate mouse models, provides an opportunity to elucidate the role that the gene plays in normal physiology. However, studies of human disease provide direct insight into the effect of inactivating mutations in man. In this investigation, we have identified a one year-old boy from a consanguineous pedigree who is homozygous for deletion of the insulin receptor gene resulting in leprechaunism. Contrary to previous predictions, the complete deletion of the insulin receptor gene is compatible with life.

Insulin-like growth factor-binding protein-3 proteolysis is induced after elective surgery

The insulin-like growth factors (IGFs) are bound to several binding proteins (IGFBPs) that appear to regulate IGF transport, receptor binding, and action. The concentrations of these peptides are altered by catabolic conditions. To determine if IGF-I and IGFBP levels change after surgery, sera were obtained from 16 patients before and after cholecystectomy. Immunoreactive IGF-I measured in plasma samples from which IGFBPs had been extracted did not change postoperatively. In contrast, IGF-I determined in unextracted samples increased roughly 3-fold postoperatively, presumably due to changes in IGFBPs. Two days postoperatively, IGFBP-3 levels, determined by ligand blot, averaged 36% of preoperative values, whereas levels of IGFBP-2 and a 24,000 mol wt IGFBP did not change significantly. Similarly, by immunoblot, intact IGFBP-3 was decreased 84.2 +/- 20.2%, and a 31,000 mol wt IGFBP-3 fragment increased 57.5 +/- 47.4% postoperatively. Coincubation of postoperative, but not preoperative, sera with control sera resulted in a significant decrease in IGFBP-3 and production of proteolytic fragments. IGFBP-3 proteolytic activity in postoperative sera was markedly inhibited by antipain, Na-p-tosyl-L-lysine chloromethyl ketone, phenylmethylsulfonylfluoride, aprotinin, o-phenanthroline, and EDTA, but not by leupeptin or N-tosyl-L-phenylalanine chloromethyl ketone. This pattern of inhibition is consistent with a metal-dependent trypsin-like serine protease. We speculate that proteolysis of IGFBP-3 may alter tissue uptake of IGF-I and thereby help to counteract the catabolic state caused by surgery.

Tissue-specific expression of insulin-like growth factor binding protein-3 protease activity during rat pregnancy

The abundances of insulin-like growth factor binding proteins (IGFBPs) in sera and tissue homogenates of rats at days 12, 15, and 18 of pregnancy were determined by ligand- and immunoblotting. As in serum, IGFBP-3 was abundant in day 12 uterus, placenta, and fetuses, and decreased by day 15. On day 18 of pregnancy, IGFBP-2 was predominant and IGFBP-3 was less than 25% of day 12 values in fetus and placenta, and was undetectable in uterus and decidua. In contrast, IGFBPs in the nonreproductive tissues did not change significantly. IGFBP-3 was more abundant in muscle than heart and liver, and was not detected in lung, kidney, or brain. The decrease in IGFBP-3 in serum and reproductive tissues between days 12 and 15 of pregnancy was temporally related to the appearance of IGFBP-3 protease activity. Proteolytic activity was detectable only at low levels in brain, liver, and spleen, and was undetectable in lung, heart, muscle, and kidney. The specific protease inhibitors that blocked IGFBP-3 proteolytic activities in pregnant rat serum and decidua were virtually identical and suggested inhibition of a divalent cation-dependent tryptic-like serine protease. Furthermore, exposure of bovine IGFBP-3 (in nonpregnant bovine serum) or radiolabeled recombinant human IGFBP-3 to day 18 pregnant rat serum, decidua or uterus resulted in the generation of IGFBP-3 fragments with the same apparent Mrs (29-31 K and 18-23 K). We postulate that tissue-specific degradation may be as important as synthesis in determining IGFBP-3 abundance, and that the dramatic changes in IGFBPs in reproductive and fetal tissues may cause changes in IGF availability which are necessary for rapid tissue growth and differentiation.

Increased serum clearance and degradation of 125I-labeled IGF-I in protein-restricted rats

Dietary protein restriction in young rats stunts growth and decreases serum insulin-like growth factor I (IGF-I) concentrations. To investigate the possibility of a diet-induced accelerated clearance of IGF-I, the clearance of 125I-labeled IGF-I was determined by measuring the radioactivity in serum obtained at different intervals after bolus injection in 5-wk-old rats that had received either a normal 15% protein diet (P15; n = 6) or a 5% protein isocaloric diet (P5; n = 7) for 1 wk. The clearance and volume of distribution of 125I-IGF-I were increased in P5 rats by 58 and 75%, respectively, whereas the terminal elimination half-life was not changed. The calculated IGF-I production rate was decreased by 40% in P5 rats. The intermediate distribution phase (alpha) was twofold faster in P5 than in P15 animals, and 125I-IGF-I was preferentially bound to IGF binding proteins in the 40-kDa complex in P5 rats. These observations might explain the increased clearance and degradation of IGF-I in the P5 rats. Dietary protein restriction appears to lower serum IGF-I concentrations by both decreasing its production rate and increasing its clearance.

Reduced serum concentrations of insulin-like growth factor-I (IGF-I) in protein-restricted growing rats are accompanied by reduced IGF-I mRNA levels in liver and skeletal muscle

The serum concentration of insulin-like growth factor-I (IGF-I) is reduced in growing rats fed a low-protein diet, and this decrease is age-dependent, being more pronounced in younger animals. To determine whether this decrease in serum IGF-I is related to a decrease in IGF-I mRNA, growing female rats were given free access to either a 15% protein-sufficient or a 5% protein-deficient diet for 1 week. Protein restriction in 4-week-old rats decreased body weight gain by 44% (P less than 0.001 compared with 4-week controls), serum IGF-I concentration by 67% (P less than 0.001) and liver IGF-I mRNA abundance by 51% (P less than 0.001). During week 6, protein restriction for 1 week resulted in a 20% increase in food intake with no change in weight gain, a 38% reduction in serum IGF-I (P less than 0.001 compared with 6-week controls) and a 39% decrease in liver IGF-I mRNA (P less than 0.001). The serum IGF-I concentration was highly correlated (r = 0.80; P less than 0.001) with the hepatic IGF-I mRNA concentration. Skeletal muscle IGF-I mRNA abundance was also decreased significantly by protein restriction (37% at week 4, P less than 0.001, and 24% at week 6, P less than 0.01) and was closely correlated (r = 0.71; P less than 0.001) with body weight gain. Liver GH-binding protein and GH receptor mRNA abundance were reduced by 1 week of protein deprivation at week 6 but not at week 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of serum insulin-like growth factor-I (IGF-I) and IGF binding proteins during rat pregnancy

Serum concentrations of insulin-like growth factor-I (IGF-I) in rats are reduced dramatically in the latter half of pregnancy, decreasing from 1758 +/- 356 ng/ml at 12 days of pregnancy (mean +/- SD) to 761 +/- 192 ng/ml at 15 days. After parturition, IGF-I increases to nonpregnant values in 4 days. Using ligand blotting, we have demonstrated that most of the serum IGF binding proteins (IGFBPs) are concurrently reduced during pregnancy. IGFBP-3, the predominant IGFBP in nonpregnant serum, is reduced to 1.3% of nonpregnant values by 21 days of pregnancy and begins to rise within 1 h postpartum (PP). The sera of 21-day pregnant (but not nonpregnant) rats degrade IGFBP-3 in vitro, and this degradation is prevented by the protease inhibitor antipain. Decreased serum IGF-I concentrations during pregnancy, therefore, may result from reduced IGFBP-3 concentrations causing increased IGF-I clearance. In addition, steady state IGF-I mRNA and peptide levels in liver are decreased in 21-day pregnant rats (37% and 42% of 4 day PP levels, respectively), suggesting that decreased synthesis of IGF-I may also lead to lower serum IGF-I concentrations. After bolus injection, [125I]IGF-I is cleared from the serum of pregnant rats nearly 5 times faster than that of 4 day PP rats (1.21 vs. 0.25 ml/min/kg, respectively). Urinary clearance is relatively insignificant (less than 4%), and [125I]IGF-I does not cross the placenta. The intermediate distribution phase of IGF-I is slower in pregnant rats than in PP rats (t1/2 alpha, 17.1 vs. 5.4 min), whereas the terminal elimination of IGF-I is twice as fast (t1/2 beta, 228.1 vs. 106.4 min). The prolonged IGF-I distribution phase in the pregnant rats may result from decreased concentrations of 34,000 and 30,000 mol wt IGFBPs, which may transport IGF-I to tissues. The faster serum elimination half-life may result from diminished IGFBP-3, leading to greater IGF-I availability to tissues in pregnancy.

Effect of maternal fasting on fetal growth, serum insulin-like growth factors (IGFs), and tissue IGF messenger ribonucleic acids

Pregnant rats were fasted or allowed access to ad libitum feeds for the last 3 days of gestation to determine if the fetal growth retardation that results from maternal nutrient deprivation correlates with reductions in serum insulin-like growth factor-I (IGF-I) and IGF-II. In addition, IGF-I and IGF-II mRNA concentrations in liver and lung were measured by specific solution hybridization assays to determine if changes in steady state levels of mRNA correlate with changes in serum values. Fetal serum IGF-I concentrations were 30% lower in fasted than in control fetuses, although fasting did not significantly reduce the abundance of IGF-I mRNA in their livers or lungs. Serum IGF-I concentrations in the fasted dams were 34% lower than those in controls. IGF-I mRNA concentrations in the livers and lungs of the fasted dams were also lower than those in controls and correlated with serum IGF-I values (liver: r = 0.833; P less than 0.001; lung: r = 0.610; P less than 0.05). Therefore, whereas IGF-I appears to be transcriptionally regulated by fasting in dams, regulation of circulating IGF-I in fetuses may occur at a post-transcriptional step. Serum IGF-II and liver IGF-II mRNA concentrations were much higher than IGF-I levels in the fetuses and were not influenced by maternal fasting. Dam serum IGF-II concentrations were low compared to those in fetal serum and also were not reduced by fasting. We conclude that one mechanism by which maternal malnutrition causes intrauterine growth retardation is through decreased expression of IGF-I. On the other hand, short term nutrient restriction does not appear to be a regulator of IGF-II during either fetal or adult life.

Dietary protein restriction decreases insulin-like growth factor I independent of insulin and liver growth hormone binding

To determine the role of hypoinsulinemia and liver somatogenic (GH) receptors in growth retardation and decreased serum insulin-like growth factor I (IGF-I) levels during protein restriction, we have used a rat model where the effects of a low protein intake on body weight (BW), serum IGF-I concentration, and liver GH binding could be evaluated in the presence of low or high insulin concentrations. Two days after being made diabetic with streptozotocin (60 mg/kg BW), 6-week-old female rats (nine per group) were begun on a low (5%) or normal (15%) protein diet, without or with insulin supplementation (3 U lente daily). Nondiabetic rats fed both diets were used as controls (nine per group). In the nondiabetic animals, 7 days of protein restriction reduced BW gain by 50% (P less than 0.001), serum insulin by 44% (P less than 0.025), and serum IGF-I concentrations by 28% (P less than 0.001) without significantly changing liver GH binding. By day 9, BW was decreased in the diabetic animals by 12%, serum insulin by 80%, serum IGF-I by 55%, and liver GH binding by 62%; these effects were similar in the 5% and 15% protein-fed rats (P less than 0.001 vs. the corresponding controls). In the diabetes fed the normal diet, insulin treatment restored BW gain, serum IGF-I, and liver GH binding to normal values. In contrast, in the diabetics fed a protein-restricted diet and treated with insulin, BW gain and serum IGF-I concentrations remained low, similar to those in the malnourished controls. This diet-induced growth attenuation was observed despite high circulating insulin (2-3 times normal values), appropriate glucose control (63 +/- 9 mg/dl), and near restoration of liver GH binding. We conclude that while both protein restriction and diabetes attenuate growth and reduce IGF-I concentrations, the effects of protein restriction are independent of the effects of insulin and probably act by alteration of postreceptor mechanisms.

Serum concentrations of insulin-like growth factor II are not changed by short-term fasting and refeeding

To determine the factors that regulate insulin-like growth factor II (IGF-II), we raised polyclonal antibodies to this peptide and developed a RIA that measures IGF-II in serum or plasma samples after extraction of IGF-binding proteins by C18 cartridge chromatography. The IGF-II antiserum was highly specific, exhibiting no cross-reactivity with IGF-I or insulin at the highest concentrations tested (10(-6) mol/L). As little as 0.43 micrograms/L IGF-II was detectable, and 50% displacement of tracer occurred at 1.7 microgram/L. The serum IGF-II concentrations of normal adults [mean, 634 +/- 170 (+/- SD) micrograms/L], patients with acromegaly (570 +/- 146 micrograms/L), and patients with hypopituitarism (156 +/- 58 micrograms/L) were similar to those reported by others. In eight obese subjects injected with GH (0.1 mg/kg ideal BW, im, every 48 h for 16 days), serum IGF-II concentrations did not rise significantly, whereas IGF-I concentrations increased 67%. Sixteen normal subjects, within 15% of ideal body weight, were fasted for 5 days on two to four occasions and refed diets of differing protein and calorie contents. Their mean serum IGF-II concentration before fasting (691 +/- 26 micrograms/L) was not significantly different from that after fasting (674 +/- 21 micrograms/L) or after refeeding (641 +/- 20 micrograms/L). In contrast, their mean IGF-I concentration decreased 42% with fasting and rose with refeeding. Unlike IGF-I, serum IGF-II concentrations do not appear to be regulated by short term changes in nutritional status. It is clear from this study and others that IGF-II and IGF-I are regulated differently despite their structural homology and the similarity of their actions in vitro.

Crocodiles don't focus underwater

Crocodilians are amphibious reptiles which hunt prey both on land and in water. Previous refractive and anatomical studies have suggested that their eyes can focus objects in air and that their ability to refocus the eye underwater may be limited. Examination of the plane of focus of six species of crocodilians both in air and underwater has revealed that they are generally well focused in air for distant targets and severely defocused underwater. These results suggest that sensory systems other than vision must play an important role in prey capture underwater.

Different effects of intermittent and continuous growth hormone (GH) administration on serum somatomedin-C/insulin-like growth factor I and liver GH receptors in hypophysectomized rats

To determine if the pattern of GH delivery is important for the regulation of serum somatomedin-C/insulin-like growth factor I (Sm-C/IGF-I) and liver somatogenic receptors, we have measured serum Sm-C/IGF-I concentrations and free (H2O-treated homogenates) and total (MgCl2-treated homogenates) liver GH-binding sites in hypophysectomized rats treated for 7 days with rat GH (rGH), given either continuously by osmotic minipumps (50 and 250 micrograms/day) or intermittently (four sc injections of 12.5 micrograms/day). At a daily dose of 50 micrograms, intermittent rGH produced greater weight gain [+29.7 +/- 0.8 g (mean +/- SE)] than continuous GH infusion (23.3 +/- 2.0 g; P less than 0.01). Likewise, the serum Sm-C/IGF-I concentration rose more with intermittent (0.33 +/- 0.1 U/ml) than with continuous delivery (0.17 +/- 0.01 U/ml; P less than 0.01). The serum Sm-C/IGF-I level achieved with repeated GH injections was even greater than that after continuous delivery of a 5-fold higher GH dose (250 micrograms/day; 0.27 +/- 0.02 U/ml; P less than 0.05). Continuous infusions of 50 and 250 micrograms rGH/day increased the number of liver total GH receptors by 2.5-fold over that of controls. In contrast, frequent GH injections did not affect GH binding, and the serum Sm-C/IGF-I concentration did not correlate with liver GH-binding sites in the GH-injected rats (r = 0.189; P = NS). Induction of hepatic PRL receptors was 10-fold higher when GH was given continuously than when it was given intermittently. The close correlation observed between GH- and PRL-binding sites in all GH-treated rats (r = 0.955; P less than 0.001) suggests that their regulation may be linked. These data suggest that the regulatory mechanism controlling Sm-C/IGF-I production and growth might be different from those that regulate GH receptor concentrations, with GH pulses being crucial for the maximal stimulation of Sm-C/IGF and growth, but continuous exposure to GH being required for up-regulation of liver GH receptors.