Inhibition of growth hormone secretion in mild primary hyperparathyroidism

Regulation of GH and GH Signaling by Nutrients

Growth hormone (GH) and insulin-like growth factor-1 (IGF-I) are pleiotropic hormones with important roles in lifespan. They promote growth, anabolic actions, and body maintenance, and in conditions of energy deprivation, favor catabolic feedback mechanisms switching from carbohydrate oxidation to lipolysis, with the aim to preserve protein storages and survival. IGF-I/insulin signaling was also the first one identified in the regulation of lifespan in relation to the nutrient-sensing. Indeed, nutrients are crucial modifiers of the GH/IGF-I axis, and these hormones also regulate the complex orchestration of utilization of nutrients in cell and tissues. The aim of this review is to summarize current knowledge on the reciprocal feedback among the GH/IGF-I axis, macro and micronutrients, and dietary regimens, including caloric restriction. Expanding the depth of information on this topic could open perspectives in nutrition management, prevention, and treatment of GH/IGF-I deficiency or excess during life.

Growth hormone and insulin-like growth factor binding protein-1 responses to oral glucose in patients with primary hyperparathyroidism

BACKGROUND

GH and IGFBP-1 both play a role in glucose homeostasis.

OBJECTIVE

To assess the GH and IGFBP-1 responses to an oral glucose load and their relationship with glucose homeostasis in patients with primary hyperparathyroidism.

DESIGN

A cross-sectional study with a control group followed by a longitudinal study after parathyroidectomy.

PATIENTS AND METHODS

We studied 15 patients with primary hyperparathyroidism (eight women, aged 59.6 +/- 2.2 years) and nine healthy normocalcaemic controls. All subjects were ambulatory and were studied as outpatients. Glucose, insulin, GH and IGFBP-1 were measured during an oral glucose (75 g) tolerance test (OGTT).

RESULTS

Patients with hyperparathyroidism showed similar glucose responses to OGTT to those found in controls. Insulin responses were higher in patients (peak insulin 96.33 +/- 9.71 mU/l) in relation to values found in controls (58.11 +/- 9.03 mU/l; P < 0.01). Suppression of GH levels after OGTT was more marked in patients [nadir 0.03 (0.02-0.05) microg/l] than in normocalcaemic subjects [nadir GH 0.12 (0.08-0.42) microg/l; P = 0.002]. However, baseline IGFBP-1 concentration and its decrease after glucose load were similar in patients and controls. Normalization of calcium levels after parathyroidectomy was not followed by any significant changes in glucose, insulin and GH responses to OGTT. The minimum concentration of IGFBP-1 and the area under the curve (AUC) of IGFBP-1 after OGTT were higher after parathyroidectomy (3.34 +/- 0.69 microg/l and 8.94 +/- 1.72 microg x h/l, respectively) than at diagnosis (2.19 +/- 0.42 microg/l and 6.74 +/- 1.28 microg x h/l, respectively; P < 0.05). No correlation was found between PTH, calcium and phosphorus concentrations and GH and IGFBP-1 values in patients before or after normalization of calcium metabolism.

CONCLUSION

GH and IGFBP-1 do not seem to be directly involved in the hyperparathyroidism-associated changes in carbohydrate metabolism. The postoperative changes in the depression of IGFBP-1 after OGTT remain to be elucidated.