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Two muscle insulin-like growth factor-I (IGF-I) mRNA splice variants (IGF-IEa and IGF-IEb) have been identified in rodents. IGF-IEb, also called mechano growth factor (MGF) has been found to be upregulated by exercise or muscle damage. Growth hormone (GH) is the principal regulator of IGF-I expression in several tissues including skeletal muscle. Therefore, we investigated the effect of chronic GH excess or disruption of GH receptor (GHR) signalling, and the acute effect of GH administration on expression of muscle IGF-I isoforms using transgenic mice that express bovine GH (bGH), GHR gene-disrupted (GHR-/-) mice and GH-deficient lit/lit mice before and after exogenous GH administration. MGF mRNA in skeletal muscle was increased in bGH mice whereas it was decreased in GHR-/- mice compared with control animals. Exogenous GH administration to dwarf lit/lit mice significantly increased muscle MGF but not IGF-IEa mRNA 4 h after treatment. Twelve hours after GH treatment, both MGF and IGF-IEa mRNAs in muscle were increased compared with vehicle-treated lit/lit mice. In contrast in GH-sufficient lit/+ mice, both MGF and IGF-IEa mRNAs were increased 4 h after and returned to the basal level 12 h after GH treatment. Hepatic IGF-I isoforms were regulated in parallel by GH. Thus, our results demonstrated that: (1) MGF mRNA in skeletal muscle is expressed in parallel with GH action; (2) MGF mRNA in muscle is produced preferentially in the situation of GH deficiency in contrast to the pattern in the GH-sufficient state; and (3) the induction of IGF-I isoforms by GH is tissue-specific.

In serum, insulin-like growth factors (IGFs) are primarily present as a approximately 150 kDa ternary protein complex, which consists of IGFs, IGF binding protein-3 (IGFBP-3), and acid-labile subunit (ALS). Like IGF-I and IGFBP-3, serum levels of ALS depend on growth hormone (GH). To date, the diagnostic relevance of ALS in adult GH deficiency (GHD) has remained uncertain. To clarify the clinical utility of ALS measurement in adults, we measured serum ALS levels in patients with adult GHD or acromegaly. We also measured the levels of serum IGF-I and IGFBP-3 in these patients to compare the utility of ALS with IGF-I and IGFBP-3 as a marker of GH secretion. Serum ALS was measured by radioimmunoassay (RIA) kit, and serum IGF-I and IGFBP-3 were measured by immunoradiometric assay (IRMA) kits in 56 patients with adult GHD (adult-onset (AO)/child-onset (CO), 13/43) and 43 patients with acromegaly. Serum ALS levels were less than 5th percentile in 40 of 56 (71%) patients with adult GHD (32/43 (74%) for CO and 8/13 (62%) for AO), and more than 95th percentile in 38 of 43 (88%) patients with acromegaly, respectively. Serum IGF-I levels were less than -1.96 SD in 43 of 56 (77%) patients with adult GHD (35/43 (81%) for CO and 8/13 (62%) for AO) and more than +1.96 SD in 42 of 43 (98%) patients with acromegaly, respectively. Serum IGFBP-3 levels were less than -1.96 SD in 51 of 56 (91%) patients with adult GHD (42/43 (98%) for CO and 9/13 (69%) for AO) and more than +1.96 SD in 31 of 43 (72%) patients with acromegaly, respectively. These data suggested that measurement of ALS offers no advantage over measurements of serum IGF-I and IGFBP-3. Furthermore, our results indicate that serum IGFBP-3 is the most suitable marker of GH secretion for adult GHD, especially CO, while IGF-I may be the most useful in acromegaly.

Objective The purpose of this study was to survey the clinical characteristics, complications, and therapeutic outcome in patients with acromegaly. Patients and Methods The clinical features of 65 patients with acromegaly (31 males, 34 females; mean age: 50±2 yr.) who were admitted to Tokyo Women's Medical University between 1990 and 1999 were analyzed retrospectively from medical records. Results The retrospective analysis revealed that the diagnosis of acromegaly was preceded by approximately 8.1±1.1 years of signs and symptoms of the disease. Forty-six of the 65 patients (71%) had macroadenomas, 16 (25%) had microadenomas, and the remaining three had empty sella. The rate of biochemical cure or remission was 81% for microadenoma (13/16), 64% for macroadenoma without extrasellar extension (9/14), and 13% for macroadenoma with cavernous sinus extension (2/15). Eighteen (28%) patients had impaired glucose tolerance (IGT) and 32 (49%) had diabetes mellitus (DM). After treatment for acromegaly, glucose metabolism was analyzed again in 38 patients, and it improved in 26 patients with IGT or DM. Twenty-five of 65 patients (38%) had hypertension. Of 26 patients who underwent barium enema or colonoscopy, 10 had colonic polyps and 4 had colon cancer. Conclusion This study suggests that long-term excessive growth hormone (GH) secretion causes many complications. Therefore, awareness of the early symptoms and signs of acromegaly and long-term careful management of complications, along with therapy to reduce serum GH/insulin-like growth factor (IGF)-I levels, are important for patients with acromegaly.(Internal Medicine 40: 987-992, 2001)

GH plays an important role in lipid metabolism as a partitioning hormone. PPARdelta regulates lipid oxidation in skeletal muscle and is activated by several physiological ligands including fatty acids. To investigate whether GH has an effect on the regulation of transcription of PPARdelta and other genes involved in energy metabolism in skeletal muscle, mRNA levels were studied by real-time RT-PCR in lit/lit mice (isolated GH deficiency) and lit/+ mice controls (normal GH levels). Mice received either a single bolus (120 ng/g) of rat GH or vehicle, and skeletal muscle was collected 4h later. PPARdelta mRNA was increased in vehicle-treated lit/lit mice compared to vehicle-treated lit/+ mice (1.67 fold, P

The present study investigated the diurnal variation in GH receptor (GHR) mRNA in liver and skeletal muscle of 3-month-old GH-deficient and -sufficient mice using quantitative real-time RT-PCR. lit/lit (GH deficient) or lit/+ (GH sufficient) mice were fed ad libitum and lights were on between 0600 and 2000. Tissues were collected at 0800-1000, 1200-1400 and 2000-2200. Hepatic GHR mRNA levels of lit/+ mice at 0800-1000 were significantly lower than those at 1200-1400 and 2000-2200. There was no significant variation in hepatic GHR mRNA of lit/lit mice. In skeletal muscle, GHR mRNA levels of both lit/+ and lit/lit mice at 1200-1400 were significantly higher than those at 0800-1000 and 2000-2200. There was also a diurnal change in hepatic IGF-I mRNA levels of lit/+ but not of lit/lit mice; the levels were lowest at 0800-1000 in lit/+ mice. On the other hand, there was no variation in IGF-I mRNA levels in skeletal muscle. These results suggest that 1) there is a diurnal variation in GHR expression in liver and skeletal muscle and the pattern of the variation is tissue specific; 2) GH deficiency blunted the diurnal variation in GHR mRNA in liver but not that in skeletal muscle; 3) IGF-I mRNA expression in liver is more closely related to GHR mRNA expression than that in skeletal muscle.

Two muscle insulin-like growth factor-I (IGF-I) mRNA splice variants (IGF-IEa and IGF-IEb) have been identified in rodents. IGF-IEb, also called mechano growth factor (MGF) has been found to be upregulated by exercise or muscle damage. Growth hormone (GH) is the principal regulator of IGF-I expression in several tissues including skeletal muscle. Therefore, we investigated the effect of chronic GH excess or disruption of GH receptor (GHR) signalling, and the acute effect of GH administration on expression of muscle IGF-I isoforms using transgenic mice that express bovine GH (bGH), GHR gene-disrupted (GHR−/−) mice and GH-deficient lit/lit mice before and after exogenous GH administration. MGF mRNA in skeletal muscle was increased in bGH mice whereas it was decreased in GHR−/− mice compared with control animals. Exogenous GH administration to dwarf lit/lit mice significantly increased muscle MGF but not IGF-IEa mRNA 4 h after treatment. Twelve hours after GH treatment, both MGF and IGF-IEa mRNAs in muscle were increased compared with vehicle-treated lit/lit mice. In contrast in GH-sufficient lit/+ mice, both MGF and IGF-IEa mRNAs were increased 4 h after and returned to the basal level 12 h after GH treatment. Hepatic IGF-I isoforms were regulated in parallel by GH. Thus, our results demonstrated that: (1) MGF mRNA in skeletal muscle is expressed in parallel with GH action; (2) MGF mRNA in muscle is produced preferentially in the situation of GH deficiency in contrast to the pattern in the GH-sufficient state; and (3) the induction of IGF-I isoforms by GH is tissue-specific.

11Beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1) is expressed in several tissues and converts inactive glucocorticoids (GC) to active GC. 11betaHSD1 activity, evaluated by urine cortisol metabolites, is increased in patients with hypopituitarism and decreased by GH replacement. Skeletal muscle wasting is one of the major characteristics of GH deficiency (GHD). We hypothesized that increased 11betaHSD1 activity and increased GC action in skeletal muscle may play a role in the development of muscle atrophy observed in GHD patients. Glutamine synthetase (GS) mRNA in muscle has been reported to be related to GC-induced muscle atrophy. In this study, we measured mRNA levels of 11betaHSD1 and GS in skeletal muscle of GH receptor gene disrupted (GHR-/-) mice and of their age-matched wild-type mice controls to elucidate the physiological significance of 11betaHSD1 and GC in the development of GHD-associated muscle atrophy in vivo. We also measured the expression of these genes in hypertrophied muscles of giant, bovine GH transgenic mice. In skeletal muscle, although IGF-I mRNA levels were decreased in GHR-/- mice, 11betaHSD1 mRNA levels were not significantly changed compared to wild-type mice. In addition, expression level of 11betaHSD1 in muscle was lower compared to that seen in liver. GS mRNA in skeletal muscle of GHR-/- mice was not significantly different from that of controls. In bGH mice, 11betaHSD1 and GS mRNA levels were not altered compared to control mice. These data do not support a significant role of 11betaHSD1 and GC action in skeletal muscle in the development of muscle atrophy associated with GHD.

Two truncated isoforms of growth hormone (GH) receptor (GHR) were identified in mice and in humans. The proteins encoded by these isoforms lack most of the intracellular domain of the GHR and inhibit GH action in a dominant negative fashion. We have quantified the mRNAs encoding the GHR isoforms in mouse tissues by use of real-time RT-PCR and examined the effect of GH excess or deficiency on regulation of mRNA levels of the GHR isoforms in vivo. In the liver, the truncated GHR mRNAs (mGHR-282 and mGHR-280) were 0.5 and

GH has diverse biological actions that are mediated by binding to a specific, high-affinity cell surface receptor (GHR). Expression of GHR is tissue specific and a requirement for cellular responsiveness to GH. IGF-I is produced in multiple tissues and regulated in part by GH through GHR. In this study, we evaluated GHR and IGF-I mRNA expression in pituitary gland and compared the levels with those derived from liver of bovine GH transgenic, GH antagonist transgenic, lit/lit mice, and their respective controls using real-time RT-PCR. In liver, both GHR and IGF-I mRNA expressions were regulated in parallel with GH action in all three animal models, and there was a strong correlation between GHR and IGF-I mRNA levels. In the pituitary gland, increased expression of IGF-I mRNA in the pituitary of bovine GH transgenic mice was observed, whereas IGF-I expression in GH antagonist transgenic or lit/lit mice was similar to that observed in control animals. There were no differences of GHR mRNA levels in pituitary gland of any groups we examined. There was also no correlation between GHR and IGF-I mRNA levels in any group in the pituitary gland. In conclusion, we found that hepatic GHR and IGF-I mRNA levels were strongly correlated with each other in chronic GH excess or deficient state, and that regulation and correlation between local GHR and IGF-I mRNA levels induced by GH is different between liver and pituitary gland.

Atherosclerosis and insulin resistance are common complications of adult growth hormone deficiency (GHD) and acromegaly. Circulating adiponectin, an adipocyte-derived protein, has both anti-atherogenic and insulin-sensitising effects. In this study, we measured serum adiponectin levels in patients with either adult GHD or acromegaly to clarify the impact of GH secretory states on the regulation of serum adiponectin levels. Serum adiponectin level was measured by radioimmunoassay in 32 patients with adult GHD, 49 patients with acromegaly and 25 normal subjects. The relationships between adiponectin and insulin sensitivity index assessed as quantitative insulin sensitivity check index (QUICKI), BMI, and serum GH and IGF-I levels were then investigated. The values of QUICKI were significantly lower in patients with acromegaly or adult GHD compared to normal subjects (0.33 +/- 0.03, P0.01, 0.35 +/- 0.04, P0.05 and 0.36 +/- 0.01, respectively). While patients with adult GHD had significantly lower serum adiponectin levels than patients with acromegaly (6.5 +/- 3.9, 9.2 +/- 5.0, P0.01) these levels were not significantly different from those found in normal subjects (7.8 +/- 4.3 mug/ml). There was an inverse correlation between serum adiponectin levels and BMI in both patient groups (GHD r = -0.39, P0.05; Acromegaly r = -0.35, P0.05). However, serum adiponectin levels correlated positively with QUICKI (R(s) = 0.37, P0.05) only in patients with adult GHD. In patients with acromegaly, the levels of circulating adiponectin showed an inverse correlation with serum IGF-I levels (R(s) = -0.34, P0.05), but not with basal GH levels. These results demonstrate that adiponectin levels are significantly lower in patients with adult GHD than in patients with acromegaly. Adiponectin levels are similar in patients with GHD and healthy controls, whereas in patients with acromegaly, insulin resistance appears to be not closely related to adiponectin levels compared with BMI. The different relationship between adiponectin and QUICKI observed in the adult GHD and acromegaly groups presumably reflects differences in the mechanisms of insulin resistance under states of GH deficiency or excess.

Initial investigations of a 70-year-old woman with clinical Cushing's syndrome, including overnight dexamethasone suppression test, CRH test, and pituitary MRI, suggested the presence of ectopic ACTH production. Thoracic computed tomography (CT) scan revealed a mass measuring 7 mm in the right lung, but it was thought to be an incidental opacity, leaving the source of ectopic ACTH undetermined for several years. During this period, although the size of the lung opacity did not change remarkably, serum cortisol levels became elevated to 43 microg/dl, and the patient's symptoms worsened. Tl-201 SPECT demonstrated intense accumulation in the right lung. The mass was surgically resected using thoracoscopy to investigate it as the focus of ACTH production. Histological and immunohistochemical examination confirmed that the area of intense Tl-201 uptake was an ACTH-producing bronchial carcinoid. Plasma ACTH and cortisol levels decreased immediately after the surgery. In conclusion, this case demonstrated Tl-201 scintigraphy as a useful tool in identifying the location of an ACTH-producing bronchial carcinoid.