Diencephalic syndrome due to hypothalamic tumor: a model of the relationship between weight and puberty onset

Changes in body weight, statural growth rate, and puberty may be the presenting symptoms of hypothalamic-pituitary tumors.

The objective of the study was to assess the relationship between the tumor and its treatment and the weight, growth rate, and onset of puberty, using the diencephalic syndrome of emaciation as model.

Eleven patients seen before 1 yr of age, except one aged 9 yr, for diencephalic syndrome of emaciation due to hypothalamic pilocytic astrocytoma, were treated by surgical resection (n = 9), cranial irradiation (n = 7), and/or chemotherapy (n = 10).

At diagnosis, growth rate was normal, despite the emaciation, and there was no hypothalamic-pituitary deficiency, except in the oldest patient. After tumor treatment, all had GH and thyroid-stimulating hormone deficiencies, but only three, who underwent major surgical resection, also had ACTH deficiency and diabetes insipidus. Eight became obese, and all but the oldest had transient precocious puberty. Plasma leptin concentrations were very low at diagnosis, increased after tumor treatment, and decreased transiently in one boy when the testosterone increased. The plasma soluble leptin receptor concentrations changed in the opposite direction, leading to an increase in the free leptin index, including in the three patients whose tumor was reduced without surgery. The body mass index was correlated positively with plasma leptin (rho = 0.73, P = 0.0004) and free leptin index (rho = 0.63, P < 0.004) and negatively with ghrelin (rho = -0.49, P < 0.03) concentrations.

The obesity that occurs after treatment of hypothalamic tumors is not due to dysregulation of leptin secretion because it and plasma soluble leptin receptor remain regulated by factors like testosterone. This study also shows the influence of weight, possibly via leptin secretion, on the transient hypothalamic-pituitary-gonadal activation that occurs during the first year of life.