Growth hormone (GH) replacement decreases serum total and LDL-cholesterol in hypopituitary patients on maintenance HMG CoA reductase inhibitor (statin) therapy

Replacement with sex steroids in hypopituitary men and women: implications for gender differences in morbidities and mortality

Hypopituitarism is a heterogenous disorder characterised by a deficiency in one or more anterior pituitary hormones. There are marked sex disparities in the morbidity and mortality experienced by patients with hypopituitarism. In women with hypopituitarism, the prevalence of many cardiovascular risk factors, myocardial infarction, stroke and mortality are significantly elevated compared to the general population, however in men, they approach that of the general population. The hypothalamic-pituitary-gonadal axis (HPG) is the most sexually dimorphic pituitary hormone axis. Gonadotropin deficiency is caused by a deficiency of either hypothalamic gonadotropin-releasing hormone (GnRH) or pituitary gonadotropins, namely follicle-stimulating hormone (FSH) and luteinising hormone (LH). HPG axis dysfunction results in oestrogen and testosterone deficiency in women and men, respectively. Replacement of deficient sex hormones is the mainstay of treatment in individuals not seeking fertility. Oestrogen and testosterone replacement in women and men, respectively, have numerous beneficial health impacts. These benefits include improved body composition, enhanced insulin sensitivity, improved atherogenic lipid profiles and increased bone mineral density. Oestrogen replacement in women also reduces the risk of developing type 2 diabetes mellitus. When women and men are considered together, untreated gonadotropin deficiency is independently associated with an increased mortality risk. However, treatment with sex hormone replacement reduces the mortality risk comparable to those with an intact gonadal axis. The reasons for the sex disparities in mortality remain poorly understood. Potential explanations include the reversal of women's natural survival advantage over men, premature loss of oestrogen's cardioprotective effect, less aggressive cardiovascular risk factor modification and inadequate oestrogen replacement in women with gonadotropin deficiency. Regrettably, historical inertia and unfounded concerns about the safety of oestrogen replacement in women of reproductive age have impeded the treatment of gonadotropin deficiency.

Effects of adult growth hormone deficiency and replacement therapy on the cardiometabolic risk profile

Adult growth hormone deficiency (AGHD) is considered a rare endocrine disorder involving patients with childhood-onset and adult-onset growth hormone deficiency (AoGHD) and characterized by adverse cardiometabolic risk profile. Besides traditional cardiovascular risk factors, endothelial dysfunction, low-grade inflammation, impaired adipokine profile, oxidative stress and hypovitaminosis D may also contribute to the development of premature atherosclerosis and higher cardiovascular risk in patients with AGHD. Growth hormone replacement has been proved to exert beneficial effects on several cardiovascular risk factors, but it is also apparent that hormone substitution in itself does not eliminate all cardiometabolic abnormalities associated with the disease. Novel biomarkers and diagnostic techniques discussed in this review may help to evaluate individual cardiovascular risk and identify patients with adverse cardiometabolic risk profile. In the absence of disease-specific guidelines detailing how to assess the cardiovascular status of these patients, we generally recommend close follow-up of the cardiovascular status as well as low threshold for a more detailed evaluation.

Growth hormone therapy in adults with growth hormone deficiency: a critical assessment of the literature

PURPOSE

Growth hormone (GH) therapy has been studied as treatment for clinical manifestations of adult-onset growth hormone deficiency (AO-GHD), including cardiovascular risk, bone health, and quality of life. Patients with AO-GHD typically also have significant history of pituitary pathology and hypopituitarism, which raises the question of what proportion of their clinical presentation can be attributed to GHD alone. Currently, much of the existing data for GH therapy in AO-GHD come from uncontrolled retrospective studies and observational protocols. These considerations require careful reassessment of the role of GH as a therapeutic agent in adult patients with hypopituitarism.

METHODS

We contrast results from placebo-controlled trials with those from uncontrolled and retrospective studies for GH replacement in patients with hypopituitarism. We also examine the evidence for the manifestations of AO-GHD being attributed to GHD alone, as well as the data on adults with congenital, life-long untreated isolated GHD.

RESULTS

The evidence for increased morbidity and mortality in hypopituitary patients with GHD, and for the benefits of GH therapy, are conflicting. There remains the possibility that the described clinical manifestations of AO-GHD may not be due to GHD alone, but may also be related to underlying pituitary pathology, treatment history and suboptimal hormone replacement.

CONCLUSIONS

In the setting of inconsistent data on the benefits of GH therapy, treatment of AO-GHD remains an individualized decision. There is a need for more randomized, placebo-controlled studies to evaluate the long-term outcomes of GH therapy in adults with hypopituitarism.

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.

The influence of a long-term growth hormone treatment on lipid and glucose metabolism: a randomized trial in short Japanese children born small for gestational age

Background

Long-term growth hormone (GH) treatments in short children born small for gestational age (SGA) restore lipid metabolism, but also increase insulin resistance. The aim of this study was to evaluate the influence of long-term GH therapy on lipid and glucose metabolism as well as its dose dependency in short Japanese children born SGA.

Methods

Eighty Japanese children with a short stature who were born SGA participated in this study; 65 were treated with fixed GH doses of 0.033 (low) or 0.067 (high) mg/kg/day for 260 weeks; 15 were untreated controls in the first year and were randomized to one of the two treatment groups at week 52. Serum cholesterol, glucose and insulin levels were regularly measured. An oral glucose tolerance test (OGTT) was conducted annually.

Results

The mean age at the start of GH therapy was approximately 5.3 years. Serum total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in the high dose group significantly decreased over time during GH therapy. In both dose groups for TC, and in the high dose group for LDL-C, the higher the baseline values, the greater the decrease after 260 weeks. The rate of the decrease observed after 260 weeks in patients with high LDL-C levels was greater in the high dose group. Based on the results of OGTT, no patient was classified as being diabetic; however, annual increases were observed in post-OGTT insulin levels. After 260 weeks, the homeostasis model assessment as an index of insulin resistance (HOMA-IR) increased, suggesting that insulin resistance developed over time with the GH treatment, while 36.6 % of the subjects entered puberty.

Conclusions

Long-term continuous GH treatment for children born SGA may have a potentially beneficial effect on several parameters in lipid metabolism and does not adversely affect glucose metabolism.

Trial registration

GHLIQUID-1516, GHLIQUID-1517, Japan Pharmaceutical Information Center Clinical trial registration: JapicCTI-050132. Registered 13 September 2005. Retrospectively registered. JapicCTI-050137. Registered 13 September 2005. Retrospectively registered. ClinicalTrials.gov trial registration: NCT00184717. Registered 13 September 2005. Retrospectively registered.

Adult growth hormone deficiency: current concepts

The clinical syndrome of adult growth hormone deficiency (AGHD) was widely recognized in the 1980s. In this review, we first describe the clinical features and diagnosis of AGHD and then state the effects of growth hormone (GH) therapy for these patients. The main characteristics of AGHD are abnormal body composition, dyslipidemia, insulin resistance, and an impaired quality of life (QoL) due to decreased psychological well-being. For diagnosing AGHD, the international consensus guidelines have suggested that an insulin tolerance test (ITT) is the gold standard, but in Japan, the growth hormone releasing peptide-2 (GHRP-2) test is available and is recommended as a convenient and safe GH stimulating test. The cut-off for diagnosing severe AGHD is a peak GH concentration of 9 g/L during the GHRP-2 test. Since 2006, GH therapy has been approved for Japanese patients with severe AGHD. For adults, GH replacement therapy should be initiated at a low dose (3 g/kg body weight/day), followed by individualized dose titration while monitoring patients' clinical status and serum insulin-like growth factor-I (IGF-I) concentrations. A variety of favorable effects of GH replacement have been indicated; however, it has not yet been established fully whether there is a direct effect of GH treatment on reducing mortality.

Adult growth hormone deficiency - benefits, side effects, and risks of growth hormone replacement

Deficiency of growth hormone (GH) in adults results in a syndrome characterized by decreased muscle mass and exercise capacity, increased visceral fat, impaired quality of life, unfavorable alterations in lipid profile and markers of cardiovascular risk, decrease in bone mass and integrity, and increased mortality. When dosed appropriately, GH replacement therapy (GHRT) is well tolerated, with a low incidence of side effects, and improves most of the alterations observed in GH deficiency (GHD); beneficial effects on mortality, cardiovascular events, and fracture rates, however, remain to be conclusively demonstrated. The potential of GH to act as a mitogen has resulted in concern over the possibility of increased de novo tumors or recurrence of pre-existing malignancies in individuals treated with GH. Though studies of adults who received GHRT in childhood have produced conflicting reports in this regard, long-term surveillance of adult GHRT has not demonstrated increased cancer risk or mortality.

Diagnosis and treatment of growth hormone deficiency in adults

The availability of synthetic recombinant human growth hormone (GH) in potentially unlimited quantities since the 1980s has improved understanding of the many nonstatural effects of GH on metabolism, body composition, physical and psychological function, as well as the consequences of GH deficiency in adult life. Adult GH deficiency is now recognized as a distinct if nonspecific syndrome with considerable adverse health consequences. GH replacement therapy in lower doses than those used in children can reverse many of these abnormalities and restore functional capacities toward or even to normal; if dosed appropriately, GH therapy has few adverse effects. Although some doubts remain about possible long-term risks of childhood GH therapy, most registries of adult GH replacement therapy, albeit limited in study size and duration, have not shown an increased incidence of cancers or of cardiovascular morbidity or mortality.

Limited effects of growth hormone replacement in patients with GH deficiency during long-term cure of acromegaly

The aim of this study was to assess the effects of replacement with recombinant human growth hormone (rhGH) in patients with GH deficiency (GHD) after treatment of acromegaly. Intervention study. Sixteen patients (8 men, age 56 years), treated for acromegaly by surgery and radiotherapy, with an insufficient GH response to insulin-induced hypoglycaemia, were treated with 1 year of rhGH replacement. Study parameters were assessed at baseline and after 1 year of rhGH replacement. Study parameters were cardiac function, body composition, bone mineral density (BMD), fasting lipids, glucose, bone turnover markers, and Quality of Life (QoL). During rhGH replacement IGF-I concentrations increased from -0.4 +/- 0.7 to 1.0 +/- 1.5 SD (P = 0.001), with a mean daily dose of 0.2 +/- 0.1 mg in men and 0.3 +/- 0.2 mg in women. Nonetheless, rhGH replacement did not alter cardiac function, lipid and glucose concentrations, body composition or QoL. Bone turnover markers (PINP and beta crosslaps) levels increased (P = 0.005 and P = 0.021, respectively), paralleled by a small, but significant decrease in BMD of the hip. The beneficial effects of rhGH replacement in patients with GHD during cure from acromegaly are limited in this study.

GH replacement reduces increased lipid peroxidation in GH-deficient adults

BACKGROUND

GH replacement improves numerous metabolic abnormalities in GH-deficient patients; increased lipid peroxidation (LPO) has been observed in GH-deficient patients; however, it is unknown if LPO is influenced by GH replacement.

AIM AND METHODS

To evaluate the extent to which GH replacement might reverse the increased LPO in GH-deficient adults and to analyse if this phenomenon might be involved in the improvement of metabolic disturbances due to GH treatment. Serum concentrations of malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA), as an index of LPO, were measured at baseline, and after 12 and 24 months of GH replacement in 40 adult patients with severe GH deficiency (both in adult- and childhood-onset) and in 40 healthy volunteers, matched for sex, age and body mass index (BMI). Correlations were evaluated between LPO and lipids, IGF-I, metalloproteinase-2 and -9 (MMP-2, -9), vascular endothelial growth factor (VEGF), BMI and GH dose.

RESULTS

LPO values in GH-deficient patients were several-fold higher than in controls [55.36 +/- 2.27 vs. 4.19 +/- 0.42 nmol/mg protein (mean +/- SEM), P < 0.0001] and decreased significantly over time with GH replacement to 38.61 +/- 2.15 nmol/mg protein (i.e. by approximately 30%), though still remaining markedly elevated compared with controls (P < 0.0001). The proatherogenic lipid profile parameters correlated positively with LPO in the childhood-onset subgroup before GH replacement. GH replacement restored the positive correlation between LPO and age in male patients (r = 0.57, P = 0.013; r = 0.8, P < 0.001, at 12 and 24 months of GH replacement, respectively).

CONCLUSIONS

GH replacement partially reverses the grossly abnormal LPO in GH-deficient adults. It is highly probable, therefore, that oxidative mechanisms are involved in the overall improvement of metabolic changes due to GH replacement.