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.

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.

Abstract. The purpose of this study carried out at a single institute in Japan was to investigate the clinical characteristics and complications of patients with adult growth hormone deficiency (GHD). Clinical and biochemical data of 110 patients (50 males, 60 females; mean age 42 ± 17 yr) with adult GHD who attended Tokyo Women's Medical University between 1990 and 1999 were analyzed retrospectively from medical records. This retrospective analysis demonstrated that 109 patients had multiple pituitary hormone deficiencies, with 98 patients having a deficiency of more than three hormones. Sixty-one patients had childhood onset GHD (COGHD) while the remaining 49 patients had adulthood onset GHD (AOGHD). Body mass index (BMI) ranged from 16.9 to 35.9 with a mean of 23.9 ± 4.1 (kg/m 2 ), with BMI being ≥25 kg/ m 2 in 38 patients (31% of COGHD and 38% of AOGHD). Forty-one percent of the patients had hypercholesterolemia, 41% had hypertriglyceridemia, 47% had decreased levels of HDL cholesterol and 48% had increased levels of LDL cholesterol. Intima-media thickness (IMT) of the carotid arteries was investigated in 33 patients, with abnormal findings including increased IMT or plaque being observed in 4 of 18 COGHD patients and 4 of 15 AOGHD patients. Diabetes mellitus and impaired glucose tolerance was found in 4 COGHD patients and 16 AOGHD patients. Insulin resistance was assessed in 36 patients by the homeostasis model insulin resistance index (HOMA-R) and ranged from 0.65 to 10.58 with a mean of 2.80 ± 0.37. This mean value of HOMA-R was significantly greater than that measured in normal subjects (1.58 ± 0.05: P<0.05). These data suggest that abnormal lipid and glucose metabolism, and atherosclerotic changes occur frequently in adult patients with GHD. Insulin resistance may play a role in glucose and lipid metabolism disorders associated with GHD.

Objective The purpose of this study was to survey the clinical characteristics, complications, and therapeutic outcomein 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. Fortysix 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 whounderwentbarium enemaor 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 symptomsand signs of acromegaly and long-term careful managementof 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)

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