The blurring of the margins of endocrinology and its relevance to the paediatric endocrinologist

Abstract

The word hormone was coined a century ago by Baylissand Starling when they described the discovery ofsecretin (1, 2). Coupled with the knowledge thathormones were chemical messengers produced at onesite but mediating their actions at a distal site, thespecialty of endocrinology has traditionally focussed ondiseases associated with endocrine glands producingeither excessive or inadequate amounts of hormone.Later, it became apparent that a range of disorders weredue to hormone resistance, characterised by lack ofresponse to a hormone despite normal or usuallyincreased circulating concentrations of the cognatehormone (3). Disorders of the mainstream endocrineglands (pituitary, thyroid and parathyroids, adrenals,gonads and pancreas) still provide the basis for thesyllabus in endocrinology, but now enhanced by theemergence of other organs that also produce hormones.These include the heart, lungs, kidneys, liver, gut andbrain. To this list must be added the skin (the largestorgan in the body), the vascular endothelium, bone andcartilage and fat tissue.Adipose tissue has assumed prime of place inendocrinology with the emergence of obesity as amajor disease affecting a large proportion of thepopulation. The adipocyte is a veritable factory ofhormones producing adipokines such as leptin, resistinand adiponectins. How these relate to appetite controland metabolic balance is now the subject of massiveresearch not only in basic endocrinology, but also in thepharmaceutical industry. How does the paediatricendocrinologist relate to this widening of the boundariesto endocrinology?Paediatric endocrinology as a specialty is a relativenewcomer on the endocrine scene and indeed, nurturedby a non-paediatric physician. The textbook realised byLawson Wilkins etal.on the diagnosis and managementof treatment of endocrine disorders in childhood andadolescence (4) remains a classic of clinical descriptionseven if it is long outdated on the biochemical aspects ofthe subject. The study of growth and puberty hasalways signalled out the paediatrician from the adultendocrinologist. Since growth is generally an indicatorof health and well being in infants and children, theclinical practice of the paediatric endocrinologist islocked in to mainstream paediatrics. Seldom does thepaediatric endocrinologist ‘stray’ into the territory of theadult endocrinologist for clinical practice or vice versa.That must be so inviewof the different skills and trainingneeded to practice at different points of the age span. Theadult physician would not be expected to manage theinfant with ambiguous genitalia of the newborn anymore than the paediatrician would be expected tograpple with a complexcase of acromegaly. Nevertheless,the boundaries of endocrinology are now becoming soblurred that it is incumbent on endocrinologists ofwhatever ilk to at least be aware of the mushroomingbreadth of the subject and consider facets that may berelevant to individual clinical practice.Take, for example, the concept of programmed eventsactivated in foetal life or in early infancy and then onlymanifest in some measurable format in adult life. Thephenomenon now considered under the umbrella titleof ‘developmental origins of adult disease’ (5) trans-cends virtually the whole of clinical medicine. Its originis within the purview of the paediatric endocrinologist,who is knowledgeable about the causes of foetal growthrestraint, its consequences at birth and early infancy,whether it is followed by catch-up growth or not, andhow this may affect puberty thereafter. Yet, it is still notpossible to determine precisely what triggers puberty inhumans at around 10–11 years of age. Each review ofthe subject over the past 20 years has made someheadway in completing the jigsaw, the most recentadding the GPR54 kisspeptin receptor and environ-mental chemicals to the multi-component model of thecontrol of the onset of puberty (6). The paediatricendocrinologist in clinical practice is not party to theadult consequences of foetal growth restraint asmanifested by the metabolic syndrome and subsequentcardiovascular disease. Indeed, the associations withfoetal growth stretch beyond the classic metabolicsyndrome to include reproductive abnormalities, somecancers and certain psychiatric diseases. This broad-ening of the horizon by viewing with a wide-angle lensis the concept developed in the programming for the‘Fourth Ferring Pharmaceuticals Paediatric Endo-crinology Symposium’ and recorded in print in this