Vol. 10.4
June 2013
Pituitary Adenomas in Childhood and Adolescence
Suzanne Jackman MD and Frank Diamond MD, Pediatric Endocrinology, All Children’s Hospital, St Petersburg, Florida
Abstract
Scientific advances are revealing the complexity of pituitary development, which i s cont r o l led by multiple trans c r i p t i o n factors and signaling molecules. Unregulated pituitary cell growth, resul t ing in pituitary adenoma, is usually sporadic and results from monoclonal expansion of a single mutated cell. However, some adenomas develop as part of a genetic syndrome. Prolactinoma is the most common hormonally active pituitary adenoma in children. The non-functioning (non-secreting) pituitary adenoma is the second most common and often stains positive for GH, PRL, and/or TSH. While Cushing disease, resulting from an ACTH-secreting adenoma, commonly manifests as weight gain with growth deceleration i n children, GH excess causes gigantism with rapid, accelerated growth inappropriate for the height of the family. TSH secreting pituitary adenomas are rare, and biochemical analysis will show an elevated thyroxine level with a non-suppressed o r high TSH. Though the natural h i s t o r y o f pituitary incidentalomas in children is unknown, adult practice guidelines are established.
Ref: Ped. Endocrinol. Rev. 2013;10(4): 450-459
Key Words: pituitary, adenoma, tumor, children, adolescents, pituitary development, prolactinoma, nonfunctioning adenoma
IGF-I Deficiency and Hearing Loss: Molecular Clues and Clinical Implications
Isabel Varela-Nieto1,2,3 PhD, Silvia Murillo-Cuesta1,2,3 PhD, Lourdes Rodríguezde la Rosa1,2,3 PhD, Luis Lassaletta1,2,3,4 PhD MD, Julio Contreras1,2,3,5 PhD
Abstract
Sensorineural hearing loss is a clinical heterogeneous disorder and a significant health-care problem wit h tremendous soc io-economic impact. According to WHO, “Over 5% of the world’s population has disabling hearing loss -328 million adults and 32 million children-”. In children, early hearing loss affects language acquisition. Hearing deficits are generally associated with the loss of the sensory “hair” cells and/or neurons caused by primary genetic defects or secondary to environmental factors including infections, noise and ototoxic drugs. Hearing loss cannot be reversed and currently the available treatment is limited to hearing aids and cochlear implants. Studies are being conducted to develop alternative treatments combining both preventive and reparative strategies. Human insulin like growth factor (IGF) I deficiency is a rare disease associated with hearing loss, poor growth rates and mental retardation (ORPHA73272, OMIM608747). Similarly, Igf1−/− mice are dwarfs with poor survival rates and congenital profound sensorineural deafness. IGF-I is known to be a neuroprotective agent that maintains cellular metabolism, activates growth, proliferation and differentiation, and limits cell death. Here we will discuss the basic mechanisms underlying IGF-I actions in the auditory system and their clinical implications to pursue novel treatments to ameliorate hearing loss.
Ref: Ped. Endocrinol. Rev. 2013;10(4): 460-472
Keywords: auditory neurons, deafness, IGF1R, IGF system, sensory impairment.
Novel Mechanisms of Regulation of IGF-1R Action: Functional and Therapeutic Implications
Claire Worrall1, PhD, Daniela Nedelcu1, 2 ,MSc, Julianna Serly1 ,PhD, Naida Suleymanova1 M.D., Iulian Oprea1 MD, PhD, Ada Girnita1,3 ,MD, PhD, Leonard Girnita1 MD, PhD
Abstract
The IGF-1R pathway is essential for the initiation and progression of many cancers. In contrast to other receptor tyrosine kinases involved in cancer, it is not frequently mutated or amplified. The classical model of signaling through the IGF-1R centers on ligand initiated kinase activation, allowing binding of adaptor molecules and downstream activation of the MAPK and PI3K pathways. The signaling is terminated through receptor ubiquitination and subsequent degradation. To date, therapies targeting IGF-1R have been designed solely aiming to block phosphorylation mediated signaling by preventing receptor-ligand interaction or by limiting kinase activation. Yet, the classical model is insufficient to explain receptor behavior induced by some IGF-1R inhibitors. This review advocates an updated model of IGF-1R signaling, accommodating the “classical” kinase signaling and the IGF-1R-kinase independent signaling thus providing the theoretical background for receptor downregulation induced by IGF-1R inhibitors. This model should be considered for future design of effective therapies targeting the IGF-1R pathway.
Ref: Ped. Endocrinol. Rev. 2013;10(4): 473-484
Key Words: IGF-1R, beta-arrestins, ubiquitination, cancer, GRK, biased agonism
Vitamin D in Childhood Cancer: A Promising Anticancer Agent?
D Bahar Genc1 MD, M Alp Ozkan2 MD, Atilla Buyukgebiz3 MD
Abstract
Children diagnosed and treated for cancer are vulnerable to Vitamin D defic iency depending on many factors. The Vitamin D status in children with cancer has been mostly regarded as a contributory factor for skeletal pathologies so far. However, the calcitriol was found to promote cell differentiation, inhibit malignant prol i f e r a t ion , a n d e x h i b i t a n t i - inflammatory, proapoptotic and antiangiogenic p rop e r t ies . I n a d d i t ion to t h i s , n ume rous epidemiological studies link Vitamin D and cancer and indicate to possible role of Vitamin D in cancer pathogenesis and progression. This article aims to provide an overview of the possible role of Vitamin D deficiency in childhood cancer in terms of prevention and treatment.
Ref: Ped. Endocrinol. Rev. 2013;10(4): 485-493
Key words: Vitamin D, childhood cancer, prevention, treatment
Pediatric Endocrinology Reviews (PER) ● Volume 10 ● No 4 ● July 2013 485
Determination of C-Peptide in Children: When is it Useful?
REJ Besser BSc MBBS (Hons) BSc MBBS (Hons) MRCPCH PhD, Peninsula NIHR Clinical Research Facility, Peninsula Medical School, University of Exeter, UK
Abstract
Diabetes resul ts f rom insul in defic iency b ut d e s p i t e t h i s e n d o g e n ous i n sul i n s e c r e t i o n i s i n f re q ue n t l y measur e d . C-peptide is not present in synthetic insulin so it’s presence indicates endogenous secretion. One of the key roles for measuring C-peptide in childhood is to assist in the diagnosis of diabetes subtypes, which in turn determines appropriate management. It is also useful in Type 1 diabetes to monitor d isease course, bot h i n c l i n i c a l practice and in trials following intervention with disease modifying agents. Measuring C-peptide routinely in Type 1 diabetes provides valuable information to the patient and clinician about glucose variability, risk of hypoglycemia and ketoacidosis. Newer more practical methods of C-peptide determination are now avai lable to allow assessment of endogenous insulin secretion i n routine c l i n i c a l prac t i c e . We review t he physiology of insul in secretion, the essential roles and methods for C-peptide determination in blood and in urine.
Ref: Ped. Endocrinol. Rev. 2013;10(4): 494-502
Key Words: C-peptide, type 1, type 2, diabetes, MODY, honeymoon, partial remission