Shinji Sawano

Pharmacokinetic models of insulin were examined in order to describe a plasma concentration-time profile after subcutaneous (s.c.) administration of insulin to the patients with insulin-dependent diabetes mellitus (IDDM) or non-insulin-dependent diabetes mellitus (NIDDM). Diabetic subjects were restricted to those with fasting plasma insulin levels around the lowest limit for insulin assay (5 microU/ml). A one-compartment open model with first-order absorption and elimination was appropriate for estimating the plasma concentration-time profile of insulin injected or infused subcutaneously. In the case of continuous s.c. insulin infusion (CSII) for 1 h at the rate of 3 ml/h (2--3 U/ml), the absorption rate constant (Ka), elimination rate constant (Ke), and distribution volume (Vd) were 0.026 +/- 0.001 min-1 (mean +/- SEM; absorption half-life: 27 min), 0.013 +/- 0.005 min-1 (elimination half-life: 53 min), and 1.99 +/- 0.49 L/kg body wt, respectively. These values did not differ significantly from those generated by single bolus s.c. injection of undiluted insulin (40 U/ml). The calculated areas under the plasma insulin concentration-time curves from time zero to infinity ([AUC] 0 infinity) did not differ after each mode of administration, while the [AUC] 0 infinity after CSII was about 32% of that following intravenous bolus injection (P less than 0.01). The following conclusions can be drawn from these results: (1) the plasma concentration-time profile of insulin after CSII or bolus s.c. injection can be analyzed by pharmacokinetic modeling, (2) the absorption kinetics of insulin did ot differ significantly between two modes of s.c. insulin administration in the patients with IDDM or NIDDM, and (3) the insulin after CSII or single bolus s.c. injection seems to be degraded at the s.c. site to the same extent.

In this study, we compared the clinical and endocrinological characteristics, neuroimaging findings, surgical outcome, and conventional histological findings (including immunohistochemistry) with the electron microscopic appearance of 31 growth hormone (GH)-producing adenomas. By electron microscopy, these 31 tumors were divided into 23 densely granulated somatotroph adenomas (DG adenomas) and 8 sparsely granulated somatotroph adenomas (SG adenomas). SG adenomas more frequently affected younger women, but no significant correlation was found between the adenoma type and the characteristic signs and symptoms of acromegaly, the incidence of diabetes mellitus or hypertension, or the basal serum GH and insulin-like growth factor I levels. A distinct response of GH to thyrotropin-releasing hormone, bromocriptine, or GH-releasing hormone was significantly more common in patients with DG adenomas than in those with SG adenomas, whereas the incidence of a response to gonadotropin-releasing hormone or oral glucose was not significantly different between the two groups. An analysis of neuroimaging findings and surgical results indicated that SG adenomas were more likely to be macroadenomas with suprasellar extension or invasive tumors and had a lower surgical cure rate. However, postoperative radiotherapy seemed to be similarly effective in both types of adenoma to prevent a tumor recurrence and to reduce postoperative GH basal level in serum. Light microscopy showed that DG adenomas were mainly acidophilic and were immunopositive not only for GH but also for prolactin (43%), the beta subunit of thyroid-stimulating hormone (26%), and the alpha subunit of glycoprotein hormone (87%), whereas SG adenomas were almost all chromophobic and only revealed immunopositivity for GH.(ABSTRACT TRUNCATED AT 250 WORDS)

OBJECTIVE: Sixty-one of 83 patients with acromegaly treated between 1969 and 1993 were analysed retrospectively to clarify which early postoperative factors were significant predictors of a successful long-term outcome and which preoperative factors significantly influenced the early postoperative results. PATIENTS: Of the 61 patients, 30 were operated on before 1987 and 31 afterwards. A successful long-term surgical outcome was defined as a long-term mean basal GH level < 6 mU/l (comparable to < 3 micrograms/l), a normal IGF-I level, and normal GH dynamics. RESULTS: Overall, 59% of patients (37% before 1987 and 81% after) had an early postoperative mean basal GH level < 6 mU/l, and 56% (29% before 1987 and 77% after) met all three of the specified criteria for a successful long-term surgical outcome. Statistical analysis confirmed that GH dynamics and postoperative mean basal GH level < 6 mU/l were significant predictors of the long-term surgical outcome, whereas the postoperative IGF-I level alone was not. On the other hand, abnormal preoperative GH dynamics were normalized in all patients with a postoperative mean basal level < 6 mU/l. In addition, there were no patients showing an unsuccessful long-term outcome in those associated with both the early postoperative mean basal GH level < 6 mU/l and normalization of the IGF-I level. Therefore, measurement of the early postoperative mean basal GH level and the IGF-I level may be an economical and simple guide to predict the long-term surgical outcome. Moreover, multivariate analysis indicated that cavernous sinus invasion was an independent significant factor influencing the early postoperative outcome. CONCLUSIONS: Successful long-term surgical outcome may be predicted if early postoperative mean basal GH level is reduced to < 6 mU/l (< 3 micrograms/l) and IGF-I level becomes normal. This study also confirms that early diagnosis and treatment by an experienced endocrinologist and neurosurgeon can improve the operative results in patients with acromegaly.

Previous studies have shown that reserpine (1 mg/kg ip) completely blocks insulininduced growth hormone (GH) release. The possibility that the suppressive action of this drug on GH secretion might be due to its catecholaminedepleting action was investigated in the present experiments. α-Methyldopa (300 mg/kg ip), amethyl- m-tyrosine (300 mg/kg ip), or tetrabenazine (15 mg/kg ip), like reserpine, were effective in suppressing the release of GH induced by 2 U/kg of insulin. Guanethidine (30 mg/kg ip) and tyramine (15 mg/kg ip) were without effect. The blockade of GH release induced by reserpine (1 mg/kg ip) was reversed by iproniazid (150 mg/kg sc). After reserpine treatment (1 mg/kg ip), the release of growth hormone-releasing factor (GRF) from the hypothalamus induced by insulin (2 U /kg ip) was abolished. From these experiments it is concluded that: 1. The reduction of stores of brain norepinephrine impairs GH release; 2. brain amines might play a role in the release of hypothalamic neurohumoral transmitters. (Endocrinology80: 471, 1967)