Growth Hormone Deficiency

Vijayakumar Madhava
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Growth Hormone Deficiency - Abstract
Growth hormone deficiency is one of the common causes of short stature in children. Incidence of this condition is between 1in 3000-4000 live births. Diagnosis is often delayed because of lack of importance given to the art of accurate and serial measurement of height and plotting those observations in a growth chart. There is no “gold standard test” for diagnosis and clinicians have to depend upon a careful history and accurate auxological measurements for early detection. Before doing specific tests, nutritional, systemic and familial causes should be ruled out. Growth hormone replacement therapy is the treatment of choice. With the advent of recombinant technology, availability of growth hormone is not a problem but its exorbitant cost prevents many needy patients from taking this medicine.

Growth hormone is secreted by the pituitary gland, which is located at the base of the skull, in a bony cavity situated in the sphenoid bone called as sella turcica. It is attached to the hypothalamus by infundibulum and consists of two parts namely anterior adenohypophysis (anterior lobe) and posterior neourohypophysis (posterior lobe). Developmentally, anterior pituitary gland develops from Rathke’s pouch, as an invagination of oral ectoderm and posterior pituitary from neural ectoderm. Anterior pituitary gland produces 6 hormones from the 5 cell types. They are:
• Somatotrope - Growth hormone (GH)
• Lactotrope - Prolactin (PRL)
• Thyrotrope - Thyroid stimulating hormone (TSH)
• Corticotrope - Pro opio melanocortin (POMC), the precursor of adrenocorticotropic hormone (ACTH)
• Gonadotrope - Leutinizing hormone (LH), follicle stimulating hormone (FSH)
Hormones secreted by the posterior lobe of pituitary gland are produced in the supra optic and paraventricular nuclei of hypothalamus. They are oxytocin and vasopressin. Hypothalamus controls the hormonal secretion by the pituitary gland by producing various inhibitory and releasing hormones. Major hormones secreted by hypothalamus are:
• Growth hormone releasing hormone ( GHRH)
• Corticotropin releasing hormone (CRH)
• Thyrotropin releasing hormone (TRH)
• Gonadotropin releasing hormone (GnRH)
• Growth hormone inhibiting hormone ( somatostatin)
• Dopamine

Growth hormone
Growth hormone is a 191 aminoacid single chain polypeptide synthesized from the somatotropes. The gene responsible for its production ( GH1) is situated in the long arm of chromosome 17 ( q 22-24). It is secreted in a pulsatile fashion which is controlled by alternating secretion of GHRH and stomatostatin. Ghrelin, a hormone produced from the stomach and arcuate nucleus of hypothalamus also stimulates GH secretion. Various physiologic factors influencing GH synthesis and release are sleep, exercise, stress, trauma, hypoglycemia, fasting and puberty, which stimulate and hyperglycemia which inhibit its secretion and/or release. Pharmacological agents used to increase GH secretion include insulin, glucagon, clonidine, levodopa and propranolol. Peak serum GH concentrations are achieved during sleep.
Growth hormone acts by stimulating the synthesis of insulin like growth factor (IGF-1). IGF-1 is a single chain polypeptide containing 70 aminoacids, synthesized mainly from the liver and circulates binding to several binding proteins of which IGFBP3 is the most important one. Secretion of both IGF1 and IGFBP3 are regulated by GH. Hence estimation of these proteins are widely used in the diagnosis oh GH deficiency


References
Growth Hormone Deficiency Growth Hormone Deficiency 4/4/2016
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