Abstract

FISZLEJDER, L. The activity of the somatotrophic function in Functional Hypothalamic Amenorrhea (FHA) related to undernourishmant. Rev. argent. endocrinol. metab. [online]. 2011, vol.48, n.1, pp.38-50. ISSN 1851-3034.

The activity of the somatotropic function in Functional Hypothalamic Amenorrhea (FHA) is increased at the central level, and paradoxically, the peripheral hormonal behaviour, intermediate metabolism and several clinical aspects may be similar to those observed in somatotropic axis deficiency. Baseline and daily GH secretion levels are high, but its pulsatile profile is irregular. This results in resistance to GH, i.e., downregulation of hormone receptors, which, together with the decrease in GH binding protein (GHBP), impair GH ability to stimulate the synthesis of IGF-I, IGFBP-3 and the acid-labile subunit in the liver. This causes a decrease in the availability of free IGF-I in tissues. In addition, IGFBP-1 and IGF-BP2 significantly increase. Even if these peptides are regulated by GH, their inverse correlation with insulin activity (which is decreased in these patients) and the low protein diet, respectively, appear to be more important factors. The increase in the serum levels of these peptides also contributes to the decrease in free IGF-I. Alterations in secretory patterns lead to a decrease in leptin concentration (an adipokine) and to an increase in Ghrelin, which, in turn, facilitates GH secretion and has a remarkable incidence in intermediate metabolism in these undernourished patients. These hormonal changes can be interpreted as a mechanism of homeostatic adaptation tending to preserve availability of energetic nutrients. Thus, there is an initial predominance of lypolisis followed by proteolysis at muscle level. If dietary restriction continues, a process of neoglucogenesis occurs in the liver and muscle tissue, with proteins and free fatty acids (NEFAs) being used as substrates. This is followed by glucogenolysis, which produces glucose. However, the increase in NEFAs and the potential presence of ketone bodies in highly restricted diets, suggest the presence of metabolic acidosis. This clinical condition implies an increased cardiovascular risk and the possibility of premature death, a potential outcome in undernourished patients with FHA. No competing financial interests exists.

Keywords : Amenorrhea; GH; Ghrelin; GH Resistance; IGF-I.

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