d3-Growth hormone receptor polymorphism in acromegaly: effects on metabolic phenotype.

OBJECTIVE: A common polymorphic variant of the growth hormone receptor (GHR) is because of genomic deletion of exon 3 and has been linked with increased responsiveness to exogenous GH. The impact of this polymorphism in acromegaly, a disease characterized by endogenous excess of GH and partial loss of IGF-I feedback on tumoural GH secretion, is not clear. The aim of this study was to investigate possible influences of d3GHR on the GH/IGF-I relationship and metabolic parameters in acromegaly. DESIGN AND METHODS: Retrospective study on 76 acromegalic patients. Genotype analysis was carried out on leucocyte DNA by multiplex PCR assay. Clinical, hormonal and biochemical parameters at diagnosis were collected from patients' medical records. RESULTS: Forty-two patients (55.3%) were homozygotes for the allele encoding the full-length GHR (fl/flGHR), 27 patients were heterozygotes (fl/d3) and seven homozygotes (d3/d3) for the genomic deletion of exon 3. Heterozygotes and homozygotes for the d3 allele were considered together (d3GHR) and compared with fl/flGHR patients. d3GHR and fl/flGHR patients showed no difference in GH and IGF-I levels or in the relationship between these two parameters. Patients bearing d3GHR had a lower body mass index (BMI) than patients bearing fl/flGHR (25.8 +/- 2.1 vs. 28.1 +/- 4.8 kg/m(2), P < 0.05). Diabetes mellitus and hypertension were equally distributed, but more d3GHR patients had a normal glucose tolerance (66.7%vs. 56.3%, P < 0.05). The presence of d3GHR allele, and not BMI or age, was a significant negative predictor of insulin levels 120 min after oral glucose load (beta = -80.8, P < 0.05). CONCLUSIONS: This study supports the hypothesis that the d3GHR is functionally different from the fl/fl variant mostly for the effects on body weight regulation and on glucose metabolism.

Cortisol secretion in patients with type 2 diabetes: relationship with chronic complications.

OBJECTIVE: The presence of an enhanced cortisol secretion in patients with type 2 diabetes is debated. In type 2 diabetic subjects, cortisol secretion was found to be associated with the complications and metabolic control of diabetes. We evaluated cortisol secretion in 170 type 2 diabetic subjects and in 71 sex-, age-, and BMI-matched nondiabetic subjects. RESEARCH DESIGN AND METHODS: In all subjects, we evaluated ACTH at 8:00 a.m. in basal conditions and serum cortisol levels at 12:00 p.m. (F24) and at 9:00 a.m. after a 1-mg overnight dexamethasone suppression test and 24-h urinary free cortisol (UFC). In diabetic patients, we evaluated the presence of chronic complications (incipient nephropathy, asymptomatic neuropathy, background retinopathy, and silent macroangiopathy). Patients were subdivided according to the absence (group 1, n = 53) or presence (group 2, n = 117) of diabetes complications. RESULTS: In group 2, UFC (125.2 +/- 4.6 nmol/24 h) and F24 (120.6 +/- 4.1 nmol/l) were higher than in group 1 (109.2 +/- 6.8 nmol/24 h, P = 0.057, and 99.7 +/- 6.1 nmol/l, P = 0.005, respectively) and in nondiabetic patients (101.7 +/- 5.9 nmol/24 h, P = 0.002, and 100.3 +/- 5.3 nmol/l, P = 0.003, respectively). In diabetic patients, the number of complications was associated with F24 (R = 0.345; P < 0.0001) and diabetes duration (R = 0.39; P < 0.0001). Logistic regression analysis showed that the presence of diabetes complications was significantly associated with F24, sex, duration of diabetes, and glycated hemoglobin. CONCLUSIONS: In type 2 diabetic subjects, hypothalamic-pituitary-adrenal activity is enhanced in patients with diabetes complications and the degree of cortisol secretion is related to the presence and number of diabetes complications.

Hypothalamic-pituitary-adrenal activity in type 2 diabetes mellitus: role of autonomic imbalance.

Symptomatic diabetic neuropathy has been found to be associated with hypothalamus-pituitary-adrenal (HPA) axis hyperfunction, but no data are available about HPA activity in diabetic patients with asymptomatic autonomic imbalance. To evaluate HPA axis activity in patients with type 2 diabetes mellitus (T2DM) in relation to the presence or the absence of subclinical parasympathetic or sympathetic neuronal dysfunction, we performed an observational study on 59 consecutive type 2 diabetic patients without chronic complications and/or symptoms of neuropathy or hypercortisolism. The following were measured: serum cortisol at 08:00 am and at midnight (F8 and F24, respectively), post-dexamethasone suppression cortisol, 24-hour urinary free cortisol (UFC), and morning corticotropin (ACTH). Deep-breathing (DB) and LS (LS) autonomic tests were performed to assess the parasympathetic function; postural hypotension test was performed to evaluate sympathetic activity. Patients were subdivided into 4 groups: subjects with parasympathetic failure (group A), sympathetic failure (group B), both para- and sympathetic failure (group C), and without autonomic failure (group D). Hypothalamus-pituitary-adrenal activity was increased in group A compared with group D (UFC, 48.6 +/- 21.4 vs 21.6 +/- 9.8 microg/24 h, P < .0001; ACTH, 27.0 +/- 8.6 vs 15.7 +/- 5.7 pg/dL, P < .01; F8, 20.4 +/- 4.5 vs 13.6 +/- 3.8 microg/dL, P < .05; post-dexamethasone suppression cortisol, 1.2 +/- 0.4 vs 0.8 +/- 0.6 microg/dL, P < .05, respectively) and group B (UFC, 26.3 +/- 11.0 microg/24 h, P < .0001; ACTH, 19.9 +/- 8.0 pg/dL, P < .05). Regression analysis showed that UFC levels were significantly associated with the deep-breathing test (beta = -0.40, P = .004) and tended to be associated with the lying-to-standing test (beta = -0.26, P = .065), whereas body mass index, glycated hemoglobin, and duration of disease were not. Type 2 diabetic patients with asymptomatic parasympathetic derangement have increased activity of HPA axis, related to the degree of the neuronal dysfunction.

Long-term evaluation of postoperative acromegalic patients in remission with previous and newly proposed criteria.

Criteria to define remission of acromegaly have changed over years. Since 2000, criteria for cure are normal IGF-I levels and a nadir GH after oral glucose tolerance test (OGTT) of less than 1 microg/liter, although recent studies have suggested to lower this cutoff value. This study reevaluated long-term disease activity of acromegalic patients, who were previously considered in remission, using these criteria. The study included 70 of 146 patients operated on between 1984 and 1996 who were considered cured based on normal IGF-I levels, GH values less than 2.5 microg/liter, and/or disappearance of abnormal GH response to TRH/GnRH. Among these 70 patients, 16 were lost to follow-up, three died, and 11 (one of whom had disease recurrence) only gave a phone interview. Forty patients participated in the study and were reevaluated for IGF-I levels and post-OGTT GH nadir after 14.3 +/- 4.2 (mean +/- sd) yr from surgery. In all patients, normal IGF-I levels and a post-OGTT GH nadir of less than 1 microg/liter were found. In particular, 19 patients had a GH nadir of less than 0.19 microg/liter, i.e. the upper limit (mean + 2 sd) found in 30 controls, whereas 21 patients had a nadir between 0.19 and 0.77 microg/liter. No significant differences in hormonal parameters and comorbidities between the two subgroups were observed. These data showed that lowering the post-OGTT GH cutoff value within the normal range does not seem to better discriminate patients with different disease activity or long-term recurrence risk.

Association of subclinical hypercortisolism with type 2 diabetes mellitus: a case-control study in hospitalized patients.

OBJECTIVE: Subclinical hypercortisolism (SH) may play a role in several metabolic disorders, including diabetes. No data are available on the relative prevalence of SH in type 2 diabetes (T2D). In order to compare the prevalence of SH in T2D and matched non-diabetic control individuals, we performed a case-controlled, multicenter, 12-month study, enrolling 294 consecutive T2D inpatients (1.7% dropped out the study) with no evidence of clinical hypercortisolism and 189 consecutive age- and body mass index-matched non-diabetic inpatients (none of whom dropped out). DESIGN AND METHODS: Ascertained SH (ASH) was diagnosed in individuals (i) with plasma cortisol after 1 mg overnight dexamethasone suppression >1.8 microg/dl (50 nmol/l), (ii) with more than one of the following: (a) urinary free cortisol >60.0 microg/24 h (165.6 nmol/24 h), (b) plasma ACTH <10.0 pg/ml (2.2 pmol/l) or (c) plasma cortisol >7.5 microg/dl (207 nmol/l) at 24:00 h or >1.4 microg/dl (38.6 nmol/l) after dexamethasone-CRH (serum cortisol after corticotrophin-releasing hormone stimulus during dexamethasone administration) test, and (iii) in whom the source of glucocorticoid excess was suggested by imaging and by additional biochemical tests (for ACTH-dependent ASH). RESULTS: Prevalence of ASH was higher in diabetic individuals than in controls (9.4 versus 2.1%; adjusted odds ratio, 4.8; 95% confidence interval, 1.6-14.1; P = 0.004). In our population the proportion of T2D which is statistically attributable to ASH was approx. 7%. Among diabetic patients, the presence of severe diabetes (as defined by the coexistence of hypertension, dyslipidaemia and insulin treatment) was significantly associated with SH (adjusted odds ratio, 3.8; 95% confidence interval, 1.4-10.2; P = 0.017). CONCLUSIONS: In hospitalized patients, SH is associated with T2D.

Gamma-knife radiosurgery in acromegaly: a 4-year follow-up study.

Stereotactic radiosurgery by gamma-knife (GK) is an attractive therapeutic option after failure of microsurgical removal in patients with pituitary adenoma. In these tumors or remnants of them, it aims to obtain the arrest of cell proliferation and hormone hypersecretion using a single precise high dose of ionizing radiation, sparing surrounding structures. The long-term efficacy and toxicity of GK in acromegaly are only partially known. Thirty acromegalic patients (14 women and 16 men) entered a prospective study of GK treatment. Most were surgical failures, whereas in 3 GK was the primary treatment. Imaging of the adenoma and target coordinates identification were obtained by high resolution magnetic resonance imaging. All patients were treated with multiple isocenters (mean, 8; range, 3-11). The 50% isodose was used in 27 patients (90%). The mean margin dose was 20 Gy (range, 15-35), and the dose to the visual pathways was always less than 8 Gy. After a median follow-up of 46 months (range, 9-96), IGF-I fell from 805 micro g/liter (median; interquartile range, 640-994) to 460 micro g/liter (interquartile range, 217-654; P = 0.0002), and normal age-matched IGF-I levels were reached in 7 patients (23%). Mean GH levels decreased from 10 micro g/liter (interquartile range, 6.4-15) to 2.9 micro g/liter (interquartile range, 2-5.3; P < 0.0001), reaching levels below 2.5 micro g/liter in 11 (37%). The rate of persistently pathological hormonal levels was still 70% at 5 yr by Kaplan-Meier analysis. The median volume was 1.43 ml (range, 0.20-3.7). Tumor shrinkage (at least 25% of basal volume) occurred after 24 months (range, 12-36) in 11 of 19 patients (58% of assessable patients). The rate of shrinkage was 79% at 4 yr. In no case was further growth observed. Only 1 patient complained of side-effects (severe headache and nausea immediately after the procedure, with full recovery in a few days with steroid therapy). Anterior pituitary failures were observed in 2 patients, who already had partial hypopituitarism, after 2 and 6 yr, respectively. No patient developed visual deficits. GK is a valid adjunctive tool in the management of acromegaly that controls GH/IGF-I hypersecretion and tumor growth, with shrinkage of adenoma and no recurrence of the disease in the considered observation period and with low acute and chronic toxicity.

Circulating ghrelin levels in basal conditions and during glucose tolerance test in acromegalic patients.

BACKGROUND: Ghrelin exerts a wide range of metabolic functions. In contrast to the body of information accumulated on the role of ghrelin on energy balance, the possible relevance of the peptide on GH secretion in physiological and pathological conditions has so far been poorly investigated. AIM: The aim of the present study was to evaluate circulating ghrelin levels in acromegalic patients in basal conditions and in response to oral glucose tolerance test (OGTT). PATIENTS: Serum ghrelin, insulin and leptin levels were measured in 31 healthy normal weight subjects as controls, 25 patients with simple obesity and 17 non-diabetic acromegalic patients. Ghrelin and insulin response to OGTT was evaluated in six controls, four obese and six acromegalic patients. RESULTS: The acromegalic patients showed ghrelin levels lower than those observed in normal weight subjects (201+/-20 vs 329+/-32 pmol/l, P<0.05) and similar to those found in obese subjects (165+/-14 pmol/l, P=not significant). Both obese and acromegalic patients had insulin levels significantly higher than controls, while high levels of leptin were detected only in obese subjects. Serum ghrelin levels showed a significant negative correlation with insulin, leptin and body mass index (P<0.05) in normal and obese subjects. No correlation was observed in acromegalic patients, although those with severe insulin resistance showed the lowest ghrelin values (161+/-20 pmol/l). In controls and obese subjects, ghrelin levels showed a significant decrease (25-40%) during OGTT, while no effect was detectable in acromegalic patients. CONCLUSIONS: This study reports that patients with active acromegaly show low levels of circulating ghrelin that are not further reduced by OGTT, this pattern of secretion probably depending on both GH-induced insulin resistance and the putative GH/IGF-I negative feedback control on ghrelin secretion.

Effects of chronic administration of PPAR-gamma ligand rosiglitazone in Cushing's disease.

OBJECTIVE: Rosiglitazone, a thiazolidinedione compound with peroxisome proliferator-activated receptor-gamma (PPAR-gamma)-binding affinity, is able to suppress adrenocorticotropic hormone (ACTH) secretion in treated mice and in AtT20 pituitary tumor cells. These observations suggested that thiazolidinediones may be effective as therapy for Cushing's disease (CD). PATIENTS AND METHODS: Rosiglitazone (8 mg/day) was administered to 14 patients with active CD (13 women, one man, 18-68 years). Plasma ACTH, serum cortisol (F) and urinary free cortisol (UFC) levels were measured before and then monthly during rosiglitazone administration. RESULTS: In six patients a reduction of ACTH and F levels and a normalization of UFC were observed 30-60 days after the beginning of rosiglitazone administration: there was a significant difference between basal and post-treatment values for UFC (1238+/-211 vs 154+/-40 nmol/24 h, P<0.03), but not for ACTH (15.9+/-3.7 vs 7.9+/-0.9 pmol/l) and F levels (531+/-73 vs 344+/-58 nmol/l). Two of six cases, followed up for 7 months, showed a mild clinical improvement. Eight patients were nonresponders after 30-60 days of rosiglitazone treatment: their ACTH, F and UFC levels did not differ before and during drug administration. Immunohistochemical analysis of pituitary tumors removed from two responder and two nonresponder patients showed a similar intense immunoreactivity for PPAR-gamma in about 50% of cells. CONCLUSIONS: The administration of rosiglitazone seems able to normalize cortisol secretion in some patients with CD, at least for short periods. Whether the activation of PPAR-gamma by rosiglitazone might be effective as chronic pharmacologic treatment of CD needs a more extensive investigation through a randomized and controlled study.

Recombinant hGH replacement therapy and the hypothalamus-pituitary-thyroid axis in children with GH deficiency: when should we be concerned about the occurrence of central hypothyroidism?

OBJECTIVE: Recombinant hGH treatment may alter thyroid hormone metabolism and we have recently reported that 50% of patients with GH deficiency (GHD) due to organic lesions, previously not treated with thyroxine, developed hypothyroidism during treatment with recombinant human GH (rhGH). These results prompted us to evaluate the impact of rhGH treatment on thyroid function in children with GHD. DESIGN: Open study of GH treatment up to 12 months. Investigations were performed at baseline, and after 6 and 12 months of GH therapy. MEASUREMENT AND STUDY SUBJECTS: Serum TSH, FT4, FT3, AbTg and AbTPO, IGF-I, height and weight, were evaluated in 20 euthyroid children (group A) with idiopathic isolated GHD and in six children (group B) with multiple pituitary hormone deficiencies (MPHD) due to organic lesions. Among the latter, four already had central hypothyroidism and were on adequate LT4 replacement therapy, while two were euthyroid at the beginning of the study. RESULTS: Serum IGF-I levels normalized in all patients. In both groups, a significant reduction in FT4 levels (P < 0.01) occurred during rhGH therapy. No patient in group A had FT4 values into the hypothyroid range, while in four of six patients in group B, fell FT4 levels into the hypothyroid range during rhGH. In particular, the two euthyroid children developed central hypothyroidism during rhGH treatment, and their height velocities did not normalize until the achievement of euthyroidism through appropriate LT4 substitution. No variation in serum FT3 and TSH levels was recorded in either groups. CONCLUSION: Contrary to that observed in patients with MPHD, rhGH replacement therapy does not induce central hypothyroidism in children with idiopathic isolated GHD, further supporting the view that in children with MPHD, as in adults, GHD masks the presence of central hypothyroidism. Slow growth (in spite of adequate rhGH substitution and normal IGF-I levels) is an important clinical marker of central hypothyroidism, therefore a strict monitoring of thyroid function is mandatory in treated children with MPHD.