Measurement of melatonin in body fluids: Standards, protocols and procedures

Abstract: The circadian rhythm of melatonin in saliva or plasma, or of the melatonin metabolite 6‐ sulphatoxymelatonin in urine, is a defining feature of suprachiasmatic nucleus function, the endogenous oscillatory pacemaker. These measurements are useful to evaluate problems related to the onset or offset of sleep and for assessing phase delays or advances of rhythms in entrained individuals. Additionally, they have become an important tool for psychiatric diagnosis, its use being recommended for phase typing in patients suffering from sleep and mood disorders. Thus, the development of sensitive and selective methods for the precise detection of melatonin in tissues and fluids of animals emerges as necessary. Due to its low concentration and the co‐existence of many other endogenous compounds in blood, the determination of melatonin has been an analytical challenge. This review discusses current methodologies employed for detection and quantification of melatonin in biological fluids and tissues

Growth hormone during the transtion period

La etapa de transición ha sido definida como el período de la vida que comienza hacia el fin de la pubertad y finaliza cuando se adquiere la maduración adulta completa. Esta fase dura aproximadamente 6 a 8 años y durante la misma se producen una serie de modificaciones cuantitativas y cualitativas en la esfera física y psíquica, caracterizadas por la adquisición de la talla y composición corporal adulta, del pico de masa ósea, la obtención de una plena capacidad fértil y, finalmente, de las características psicosociales propias del adulto. Deben recordarse los efectos que la hormona de crecimiento (GH) ejerce a lo largo de toda la vida del sujeto sobre el metabolismo, función y estructura cardíaca, hueso, composición corporal y calidad de vida. Sin embargo, hay datos conflictivos sobre la necesidad de continuar, sin interrupción, con la terapia de GH durante la etapa de transición. Se debe tener en cuenta, también, que existe un grupo de pacientes que adquieren la insuficiencia de GH durante el período de transición. Si bien existen claras evidencias que indican no discontinuar el tratamiento luego de haber finalizado la etapa de crecimiento, los pacientes deben ser reevaluados previamente para constatar si el déficit es suficientemente severo como para justificar mantener la terapéutica con GH. La respuesta a gran parte de estas dudas podrá resolverse con estudios randomizados y observacionales a largo plazo, desarrollados por equipos multidisciplinarios especializados.148-156hugofideleff@arnet.com.arCuatrimestralTransition phase has been defined as the period of life starting in late puberty and ending with full adult maturation. This phase extends over approximately 6 to 8 years. A number of quantitative and qualitative changes occur during this phase both in physical and psychic aspects, which are characterized by attainment of adult height and body composition, peak bone mass, full reproductive potential and, finally, psychosocial characteristics inherent to adults. We should remember the effects exerted by growth hormone (GH) throughout the life of a subject on metabolism, cardiac function and structure, bone, body composition and quality of life. However, there are controversial data on the need to continue GH therapy during the transition period with no discontinuation. We should also take into account that there is a group of patients who develop GH deficiency during the transition period. Even if there is clear evidence against discontinuation of therapy after completion of the growth period, patients should be previously reevaluated to confirm if GH deficiency is severe enough to warrant continuation of GH therapy. The response to many of these issues may be obtained from long-term randomized and observational studies conducted by specialized multidisciplinary teams

Prolactinomas in Men

Prolactinomas in men have several peculiar features that distinguish them from female PRL-secreting tumors. They occur less frequently in the male gender but are usually larger, more frequently invasive, and more often aggressive than in women. Significantly higher prolactin concentrations are also observed in men as compared to women, especially in the case of macroprolactinoma. Sex differences in tumor behavior largely explain such characteristics, rather than the longer delay in making the diagnosis in men. The reasons for a more aggressive course of prolactinomas in men remain poorly understood, and some hypotheses will be discussed in this chapter. Striking differences also exist in the clinical presentation of prolactinoma. Most women will present with oligomenorrhea, infertility, and/or galactorrhea, while more than half of men initially complain from symptoms of mass effects. Male hypogonadism is often present but neglected, and the male reproductive axis appears to be less sensitive to hyperprolactinemia than the female one. Nonetheless, diagnosis of prolactinoma in men should rely on the same criteria as in women, and a similar therapeutic strategy should be used. Medical management with dopamine agonists (DA) is effective and should always be considered as the first-line therapy, also in men bearing very large and compressive tumors. Transsphenoidal surgery is indicated in patients who are either intolerant or resistant to dopamine agonists or who elect to undergo potential curative surgery. However, most male patients with a macroprolactinoma will require medical treatment to control prolactin hypersecretion after surger