The ongoing challenge of discrepant growth hormone and insulin-like growth factor I results in the evaluation of treated acromegalic patients: a systematic review and meta-analysis

OBJECTIVE

Growth hormone (GH) and insulin-like growth factor I (IGF-I) are the principal biomarkers used to assess disease activity in acromegaly, and any discrepancy between them renders interpretation of results inconclusive. Purpose of this study was to assess the frequency of this discrepancy and identify parameters that might affect its occurrence.

DESIGN

A systematic review of MEDLINE and Scopus was performed (1987-2013) followed by a meta-analysis to address the frequency of discrepant results between GH and IGF-I levels. Meta-regression and subgroup analyses were performed assessing the effects of the year of publication, the different types of GH testing and GH assays used, as well as the impact of treatment with somatostatin analogues (SSAs) on the occurrence of this discrepancy.

RESULTS

The analysis retrieved 39 eligible studies totalling 7071 patients. The pooled discordance rate between GH and IGF-I was 25·7% (95% CI: 22·3-29·4), and the predominant format was that of elevated IGF-I with normal GH levels (15·3%, 95% CI: 12·5-18·7). No significant correlation between the discordance rate and the year of publication was shown; whereas, the use of ultrasensitive GH assays resulted in higher discordance rates (30·7%, 95% CI: 25·9-35·9 vs 19·8%, 95% CI: 14·1-27·2, P = 0·04) as did treatment with SSAs (32·5%, 95% CI: 27·8-37·4) vs (21·6%, 95% CI: 17·8-25·6, P = 0·001).

CONCLUSIONS

Discrepancy between GH and IGF-I results is encountered in a quarter of treated patients with acromegaly, especially when using ultrasensitive GH assays or in patients receiving SSAs, a fact that the clinician should take into consideration when making clinical decisions.

Impact of gsp mutations in somatotroph pituitary adenomas on growth hormone response to somatostatin analogs: a meta-analysis

OBJECTIVE

Somatic mutations in the GNAS1 gene, which encodes the alpha-subunit of G stimulatory proteins (gsp), are frequently detected in somatotroph pituitary tumors and have been associated to specific clinical and histopathological characteristics. However, the question whether the presence of a somatic gsp mutation affects the response to somatostatin analog treatment remains unresolved.

DESIGN

Following a literature search, we performed a meta-analysis, including 8 eligible studies, in order to estimate the effect of gsp mutation on the percent reduction of growth hormone (GH) levels during an acute octreotide suppression test (OST). A total of 310 patients with acromegaly [126 gsp (+) and 184 gsp (-)] were included in the analysis.

RESULTS

The presence of the gsp mutation was related with a greater reduction in GH levels on OST [Weighted Mean Difference (WMD): 9.08 % (95 % CI, 2.73, 15.42); p = 0.005; random effects model]. There was significant heterogeneity for this effect estimate (I(2) = 58 %, p value for heterogeneity = 0.02). A sensitivity analysis after exclusion of a study with different methodology of OST provided similar estimates [WMD: 6.93 % (95 % CI, 1.40, 12.46); p = 0.01], albeit with no significant heterogeneity (I(2) = 35 %, p value for heterogeneity = 0.16).

CONCLUSIONS

The present meta-analysis suggests a role for gsp mutation as a prognostic factor of treatment response to somatostatin analogs.

The effect of L-thyroxine substitution on lipid profile, glucose homeostasis, inflammation and coagulation in patients with subclinical hypothyroidism

AIMS

Subclinical hypothyroidism (SH) is associated with increased risk for atherosclerosis, mainly attributable to dyslipidaemia and hypercoagulability. However, conflicting data exist regarding the effect of L-thyroxine substitution on these parameters. The purpose of this study was to assess the effect of L-thyroxine therapy on lipidaemic profile, coagulation markers, high-sensitivity C-reactive protein (hsCRP) and glucose homoeostasis in SH patients.

METHODS

It was a prospective open-label study. The following parameters were measured before and 6 months after intervention: anthropometric data, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), apolipoproteins B (apoB) and A1 (apoA1), lipoprotein (a) [Lp(a)], fasting plasma glucose and insulin, homoeostasis model assessment-insulin resistance (HOMA-IR), hsCRP, antithrombin III (AT-III), protein C (PC), protein S (PS), fibrinogen and homocysteine.

RESULTS

Thirty-two patients (30 women) aged 52.1 ± 13.9 years with SH completed the study. Baseline mean TSH levels were 6.79 ± 2.58 mIU/ml. Achievement of euthyroidism significantly reduced systolic blood pressure (BP) in patients with SH (from 135.2 ± 18.5 to 129.7 ± 15.8 mmHg, p = 0.03) and diastolic BP only in those with baseline TSH levels > 7 mIU/ml (from 79.5 ± 9.8 to 72.1 ± 7.3 mmHg, p = 0.03). No significant changes in body weight, TC, LDL-C, HDL-C, TG, apoB, glucose, insulin, HOMA-IR, hsCRP, AT-III, PC, PS, fibrinogen or homocysteine levels were noticed after restoration of euthyroidism, except for a decrease in apoA1 (p = 0.04) and an increase in Lp(a) levels (p = 0.02).

CONCLUSIONS

Except for a reduction in systolic and diastolic BP, thyroid substitution therapy does not affect lipidaemic profile, systematic inflammation, glucose homoeostasis or coagulation in patients with SH.

Oxidative stress and reduced antioxidative status, along with endothelial dysfunction in acromegaly

Acromegaly is characterized by high cardiovascular morbidity and mortality. Oxidative stress and endothelial dysfunction are underlying mechanisms of atherosclerosis.The aim of this study was to evaluate the blood redox status and endothelial function by means of nitric oxide (NO) levels in patients with acromegaly. Total antioxidant capacity (TAC), catalase activity and glutathione concentration (GSH), as measures of antioxidative capacity, total oxidized glutathione (GSSG) and thiobarbituric acid reactive substances (TBARS), as indices of oxidative stress, and NO levels were assessed in 15 patients with acromegaly (age 55.4±10.5 years; 6 males) and 15 age- and sex-matched controls (age 58.4±8.1 years; 7 males). Active disease was present in 12 patients: 11 on current pharmacotherapy and 1 newly diagnosed. Three acromegalics were in remission after successful treatment. Acromegalics as compared with controls had significantly lower levels of catalase activity (8.2±5.8 vs. 51.3±29.1 mmol/ml/min, p<0.001), GSH (0.97±0.54 vs. 1.41±0.35 mmol/l, p=0.006), GSSG (0.27±0.19 vs. 2.04±1.32 mmol/l, p=0.002) and NO levels (6.0±3.1 vs. 43.0±29.8 mmol/l, p<0.001), but higher TBARS (16.3±8.9 vs. 10.1±10.8, nmol/ml, p=0.019). After adjustment for confounders, differences in catalase activity, NO levels and TBARS remained significant (p=0.004, p<0.001 and p=0.025, respectively). No association between IGF-I/GH and oxidative stress markers was noticed, except for a positive correlation between nadir GH and GSSG (r²=0.563, p=0.036). Acromegaly is associated with increased levels of oxidative stress coupled by diminished antioxidant capacity and endothelial dysfunction indicated by the presence of decreased NO levels.

De novo autoimmune hepatitis associated with PTH(1-34) and PTH(1-84) administration for severe osteoporosis in a liver transplant patient

De novo autoimmune hepatitis (AIH) is a rare graft dysfunction occurring in patients having undergone liver transplantation (LT) for causes other than AIH. We describe for the first time a case of de novo AIH associated with the administration of parathyroid hormone 1-34 [PTH(1-34)] and PTH(1-84) for severe osteoporosis. A 61-year-old woman was referred to our metabolic bone clinic due to severe osteoporosis, 3 years after LT for primary biliary cirrhosis. Initial treatment with PTH(1-34) led to asymptomatic hypertransaminasemia (two-fold the upper limit of normal), which normalized after drug discontinuation. A new flare of transaminases (three-fold the upper limit of normal) along with elevated alkaline phosphatase was observed after administration of PTH(1-84), which did not resolve after PTH(1-84) withdrawal. Subsequently, after exclusion of common causes of liver enzyme elevation, a liver biopsy was performed. Histological findings showed de novo AIH, which responded rapidly to treatment with methylprednisolone.

Acromegaly: presentation, morbidity and treatment outcomes at a single centre

OBJECTIVE

Analysis of patients with acromegaly followed-up at a single centre, focusing on baseline characteristics, morbidity and efficacy of treatment.

DESIGN AND METHODS

Retrospective review of electronic medical records of acromegalics from 1987 to 2009.

RESULTS

One hundred and fifteen patients (45 men), aged 47 ± 14 years, with a mean follow-up of 8.8 ± 0.8 years were studied. Twenty-five per cent had micro- and 75% macroadenomas. Forty-three per cent presented with visual field defects, 49% had hypertension, 25% diabetes mellitus and 35% dyslipidaemia. At follow-up, 50% had myocardial hypertrophy, 55% colon polypodiasis, 74% nodular thyroid disease and 18% adrenal masses. Surgery was performed in 79% (8% twice), followed by conventional radiotherapy in 27%. Fifty-two per cent of the patients achieved remission. Disease control was reported in 65% of microadenomas and 41% of macroadenomas. Remission rates with surgery alone were 41%. Improvement of remission rates was achieved with subsequent treatment with somatostatin analogues (SSA) (53%), or conventional radiotherapy (63%). Nevertheless, pituitary reserve was compromised with the latter. SSA significantly improved outcomes in microadenomas, even as a monotherapy (remission in 89%), in contrast to macroadenomas (0%), although these agents were associated with impaired glucose metabolism and cholelithiasis in half of the patients.

CONCLUSIONS

Acromegaly is associated with an increased morbidity. About half of the treated patients achieved remission (2/3 of microadenomas). The best outcomes were reported for the combination of surgery with radiotherapy, in spite of a higher risk of hypopituitarism. SSA led to remission in a significant percentage of microadenomas, but was associated with increased rates of cholelithiasis and impaired glucose homeostasis.