The pituitary gland and age-dependent regulation of body composition

High Prevalence of Weight Gain in Childhood Brain Tumor Survivors and Its Association With Hypothalamic-Pituitary Dysfunction

PURPOSE

Childhood brain tumor survivors (CBTS) are at risk for developing obesity, which negatively influences cardiometabolic health. The prevalence of obesity in CBTS may have been overestimated in previous cohorts because of inclusion of children with craniopharyngioma. On the contrary, the degree of weight gain may have been underestimated because of exclusion of CBTS who experienced weight gain, but were neither overweight nor obese. Weight gain may be an indicator of underlying hypothalamic-pituitary (HP) dysfunction. We aimed to study prevalence of and risk factors for significant weight gain, overweight, or obesity, and its association with HP dysfunction in a national cohort of noncraniopharyngioma and nonpituitary CBTS.

METHODS

Prevalence of and risk factors for significant weight gain (body mass index [BMI] change ≥ +2.0 standard deviation score [SDS]), overweight, or obesity at follow-up, and its association with HP dysfunction were studied in a nationwide cohort of CBTS, diagnosed in a 10-year period (2002-2012), excluding all craniopharyngioma and pituitary tumors.

RESULTS

Of 661 CBTS, with a median age at follow-up of 7.3 years, 33.1% had significant weight gain, overweight, or obesity. Of the CBTS between 4 and 20 years of age, 28.7% were overweight or obese, compared with 13.2% of the general population between 4 and 20 years of age. BMI SDS at diagnosis, diagnosis of low-grade glioma, diabetes insipidus, and central precocious puberty were associated with weight gain, overweight, or obesity. The prevalence of HP dysfunction was higher in overweight and obese CTBS compared with normal-weight CBTS.

CONCLUSION

Overweight, obesity, and significant weight gain are prevalent in CBTS. An increase in BMI during follow-up may be a reflection of HP dysfunction, necessitating more intense endocrine surveillance.

Early versus late initiation of GH replacement in adult-onset hypopituitarism

INTRODUCTION

Adult-onset growth hormone deficiency (AGHD) is usually the last deficiency to be substituted in hypopituitarism. In children with documented GH deficiency, treatment without delay is crucial for achieving optimal effects on growth and development. In adults, it is not known whether a delay in treatment initiation influences biochemical response and the favourable physiological effects resulting from GH replacement therapy (GHRT).

METHODS

A total of 1085 GH-deficient adults from KIMS (Pfizer International Metabolic Database) were included, adequately replaced with all pituitary hormones except for GH at baseline. Patients were stratified by sex and age (20-50 years and ≥50 years) and subsequently divided into two groups below and above the median duration of unsubstituted AGHD for that subgroup. The median time of unsubstituted GHD for the total cohort was 2.53 years (P5 = 0.35, P95 = 24.42).

RESULTS

Beneficial effects of 4 years of GHRT were observed on lipids and quality of life in all subgroups. A decrease in waist circumference was observed only in older (>50 years) patients. There was no difference in IGF-I SDS and in GH dose required to normalize IGF-I in patients with a duration of unsubstituted AGHD above or below the median. No relevant differences were found between the groups for anthropometric measures, cardiovascular risk factors and quality of life scores.

CONCLUSION

In contrast to GHD in children and adolescents, no difference could be established in treatment response between early or late initiation of GHRT in AGHD in terms of required GH dose, IGF-I, metabolic health and quality of life.

Improvements in Body Composition after 4 Years of Growth Hormone Treatment in Adult-Onset Hypopituitarism Compared to Age-Matched Controls

BACKGROUND/AIMS

It is unknown whether long-term growth hormone replacement therapy (GHRT) affects body composition in an age- or sex-dependent manner. We aimed to study the effects of 4 years of GHRT on body composition in a large cohort of patients with hypopituitarism compared to a reference population matched by age and sex.

METHODS

A total of 964 GH-deficient adults from KIMS (Pfizer International Metabolic Database) with adult-onset hypopituitarism, adequately replaced with all pituitary hormones except for GH at baseline were included. A random sample of the general population (2,301 subjects) from a similar time period was used as reference. Patients and controls were grouped by sex in 5 age cohorts of 10 years. Main outcome measures were changes in BMI and waist circumference after 4 years of GHRT.

RESULTS

In younger patients (28-47 years), 4 years of GHRT resulted in a BMI increase similar to that observed in the reference population, but older patients (48-67 years) had significantly less BMI increase than age-matched healthy controls. Significant differences were seen in waist circumference in patients of all age cohorts who showed virtually no change after 4 years of GHRT compared to approximately 4 cm of increase in the reference population.

CONCLUSION

Four years of GHRT resulted in improvements in BMI and waist circumference in patients with adult-onset hypopituitarism compared to age-matched controls observed during the same follow-up time. Despite these beneficial effects on body composition, BMI and waist circumference remained higher in patients on GHRT compared to healthy controls.

Analysis of characteristics and outcomes by growth hormone treatment duration in adult patients in the Italian cohort of the Hypopituitary Control and Complications Study (HypoCCS)

PURPOSE

To examine differences in effects according to growth hormone (GH) treatment duration in adult GH-deficient patients.

METHODS

In the Italian cohort of the observational Hypopituitary Control and Complications Study, GH-treated adults with GH deficiency (GHD) were grouped by duration of treatment; ≤ 2 years (n = 451), > 2 to ≤ 6 years (n = 387) and > 6 years (n = 395). Between-group differences in demographics, medical history, physical characteristics, insulin-like growth factor-I standard deviation score (IGF-I SDS) and lipid profile at baseline, last study visit and changes from baseline to last study visit were assessed overall, for adult- and childhood-onset GHD and by gender using ANOVA for continuous variables and Chi-squared test for categorical variables.

RESULTS

At baseline, treatment duration groups did not differ significantly for age, gender, body mass index, GHD onset, IGF-I SDS, lipid profile, and quality of life. Mean initial GH dose did not differ significantly according to treatment duration group in any subgroup, except female patients, with highest mean dose seen in the longest duration group. In the longest duration group for patients overall, adult-onset patients and male patients, there were significant decreases in GH dose from baseline to last visit, and in total and low-density lipoprotein (LDL)-cholesterol concentrations. IGF-I SDS increased, to a greater extent, in the longest duration group for patients overall and female patients.

CONCLUSIONS

The results show that long-term GH treatment is associated with decreasing GH dose, increased IGF-I, decreased LDL-cholesterol and the presence of surrogate markers that help to give confidence in a diagnosis of GHD.

Adipokines (Leptin, Adiponectin, Resistin) Differentially Regulate All Hormonal Cell Types in Primary Anterior Pituitary Cell Cultures from Two Primate Species

Adipose-tissue (AT) is an endocrine organ that dynamically secretes multiple hormones, the adipokines, which regulate key physiological processes. However, adipokines and their receptors are also expressed and regulated in other tissues, including the pituitary, suggesting that locally- and AT-produced adipokines might comprise a regulatory circuit that relevantly modulate pituitary cell-function. Here, we used primary pituitary cell-cultures from two normal nonhuman-primate species [Papio-anubis/Macaca-fascicularis] to determine the impact of different adipokines on the functioning of all anterior-pituitary cell-types. Leptin and resistin stimulated GH-release, a response that was blocked by somatostatin. Conversely, adiponectin decreased GH-release, and inhibited GHRH-, but not ghrelin-stimulated GH-secretion. Furthermore: 1) Leptin stimulated PRL/ACTH/FSH- but not LH/TSH-release; 2) adiponectin stimulated PRL-, inhibited ACTH- and did not alter LH/FSH/TSH-release; and 3) resistin increased ACTH-release and did not alter PRL/LH/FSH/TSH-secretion. These effects were mediated through the activation of common (AC/PKA) and distinct (PLC/PKC, intra-/extra-cellular calcium, PI3K/MAPK/mTOR) signaling-pathways, and by the gene-expression regulation of key receptors/transcriptional-factors involved in the functioning of these pituitary cell-types (e.g. GHRH/ghrelin/somatostatin/insulin/IGF-I-receptors/Pit-1). Finally, we found that primate pituitaries expressed leptin/adiponectin/resistin. Altogether, these and previous data suggest that local-production of adipokines/receptors, in conjunction with circulating adipokine-levels, might comprise a relevant regulatory circuit that contribute to the fine-regulation of pituitary functions.

Obesity in the ageing man

As the population is ageing globally, both ageing and obesity are recognized as major public health challenges. The aim of this narrative review is to present and discuss the current evidence on the changes in body composition, energy balance and endocrine environment that occur in the ageing man. Obesity in the ageing man is related to changes in both body weight and composition due to alterations in energy intake and total energy expenditure. In addition, somatopenia (decreased GH secretion), late-onset hypogonadism (LOH), changes in thyroid and adrenal function, as well as changes in appetite-related peptides (leptin, ghrelin) and, most importantly, insulin action are related to obesity, abnormal energy balance, redistribution of the adipose tissue and sarcopenia (decreased muscle mass). A better understanding of the complex relationship of ageing-related endocrine changes and obesity could lead to more effective interventions for elderly men.

Hepatic steatosis, GH deficiency and the effects of GH replacement: a Liverpool magnetic resonance spectroscopy study

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) is reported to be more common in patients with GH deficiency (GHD) than in the general population. we aimed to determine: i) liver fat in patients with GHD compared with age and body mass index (BMI)-matched controls; and ii) effect of 6 months of GH replacement (GHR) on liver fat.

PARTICIPANTS AND METHODS

The study included 28 GHD patients and 24 controls. 12 patients were studied before and after 6 months of GHR. Anthropometry, liver enzymes and lipid profiles were measured, and body composition and intrahepatocellular lipid (IHCL) were determined by magnetic resonance imaging and spectroscopy.

RESULTS

Age and BMI (median (inter-quartile range)) of patients and controls were 52.6 (14) vs 52.6 (12) years (P=0.9) and 27.8 (24.7, 34.7) vs 27.9 (25.1, 32.1) kg/m(2) (P=0.9). IGF1 was lower in the patients (11.5 vs 16.0 nmol/l, P=0.002). There was no difference in liver transaminases, lipids or IHCL between patients and controls (2.8 (1.3, 8.6) vs 5.0 (1.5, 12.7), P=0.72), despite significantly higher visceral fat in GHD patients. Thirty-two percent of patients and 50% of controls had NAFLD (defined as IHCL >5.6%), and the relationship between IHCL and BMI was the same in each group. GHR significantly reduced abdominal subcutaneous and visceral fat in all patients; however, GHR did not reduce liver fat.

CONCLUSIONS

NAFLD is equally common in patients with GHD and matched controls. GHR is associated with a hierarchical reduction in fat deposition (fat loss: visceral > subcutaneous > liver). Further studies involving GHD patients with NAFLD are required to conclude the role of GHR in treating NAFLD.

Direct promoter induction of p19Arf by Pit-1 explains the dependence receptor RET/Pit-1/p53-induced apoptosis in the pituitary somatotroph cells

Somatotrophs produce growth hormone (GH) and are the most abundant secretory cells of the pituitary. Somatotrophs express the transcription factor Pit-1 and the dependence receptor RET, its co-receptor GFRa1 and ligand GDNF. Pit-1 is a transcription factor essential for somatotroph proliferation and differentiation and for GH expression. GDNF represses excess Pit-1 expression preventing excess GH. In the absence of GDNF, RET behaves as a dependence receptor, becomes intracellularly processed and induces strong Pit-1 expression leading to p53 accumulation and apoptosis. How accumulation of Pit-1 leads to p53 expression is unknown. We have unveiled the relationship of Pit-1 with the p19Arf gene. There is a parallel correlation of RET processing, Pit-1 increase and ARF protein and mRNA expression. Interfering the pathway with RET, Pit-1 or p19Arf siRNA blocked apoptosis. We have found a Pit-1 DNA-binding element within the ARF promoter. Pit-1 directly regulates the CDKN2A locus and binds to the p19Arft promoter inducing p19Arf gene expression. The Pit-1-binding element is conserved in rodents and humans. RET/Pit-1 induces p19Arf/p53 and apoptosis not only in a somatotroph cell line but also in primary cultures of pituitary somatotrophs, where ARF siRNA interference also blocks p53 and apoptosis. Analyses of the somatotrophs in whole pituitaries supported the above findings. Thus Pit-1, a differentiation factor, activates the oncogene-induced apoptosis (OIA) pathway as oncogenes exerting a tight control in somatotrophs to prevent the disease due to excess of GH (insulin-resistance, metabolic disease, acromegaly).

Effect of a high-protein diet on ghrelin, growth hormone, and insulin-like growth factor-I and binding proteins 1 and 3 in subjects with type 2 diabetes mellitus

We have developed a diet that over 5 weeks dramatically lowers plasma glucose in people with type 2 diabetes mellitus. This diet consists of 30% carbohydrate, 30% protein, and 40% fat and is referred to as a Low Biologically Available Glucose (LoBAG) diet. The diet also resulted in an approximately 30% increase in fasting insulin-like growth factor-I (IGF-I). Thus, we were interested in determining if the IGF-I elevation was due to an increase in ghrelin and growth hormone (GH) or to a change in IGF-I binding proteins (IGFBPs). Eight men with type 2 diabetes mellitus ingested a control diet (15% protein, 55% carbohydrate, and 30% fat) and a LoBAG(30) diet for 5 weeks in a randomized crossover design with a washout period in between. Before and after each 5-week period, subjects had blood drawn for total glycated hemoglobin and, at several time points over 24 hours, for GH, IGF-I, IGFBP-1, IGFBP-3, ghrelin, glucose, and insulin. Fasting and 24-hour glucose concentrations and total glycated hemoglobin were decreased, as expected (all Ps < .05). Fasting IGF-I increased by approximately 30% (P = .05) and remained unchanged throughout 24 hours. Ghrelin, GH, IGFBP-1, IGFBP-3, and insulin were not different between diets. Insulin and IGFBP-1 concentrations were reciprocal, as expected. Insulin-like growth factor-I binding protein 1 decreased as insulin increased to greater than approximately 30 to 40 μU/mL. Ingestion of a LoBAG(30) diet by weight-stable subjects with type 2 diabetes mellitus resulted in an increase in total IGF-I without an increase in ghrelin, GH, and IGFBP-3 or a change in IGFBP-1 regulation. The mechanism remains to be determined.