Effect of pituitary ablation on diabetic retinopathy studied by fluorescence angiography

The effect of growth hormone (GH) replacement therapy in adult patients with type 1 diabetes mellitus and GH deficiency

OBJECTIVES

Specific problems in patients with insulin-dependent diabetes mellitus (IDDM) and GH deficiency are hypoglycaemic attacks, increased insulin sensitivity and loss of energy. These problems may be related to GH deficiency.

PATIENTS

GH replacement was initiated in five patients with type 1 diabetes mellitus and GH deficiency for 6 months [four males and one female, mean age 41.6 +/- 3.8 years, mean +/- standard error of the mean (SEM); body mass index (BMI) 22.3 +/- 1.2 kg/m2].

METHODS

Body composition (bioimpedance), metabolic control [haemoglobin A1C (HbA1C)], insulin requirement and frequency of hypoglycaemia were measured, and quality of life was assessed using validated questionnaires. Monthly eye photographs were taken.

RESULTS

IGF-I concentrations were below the age-adjusted range at baseline and increased significantly following GH replacement therapy [analysis of variance (ANOVA), P < 0.05]. Diabetes control as assessed by HbA1C remained stable (8.2 +/- 0.2 vs. 8.0 +/- 0.4), but needed a 1.75-fold increase in insulin dose/day. Lean body mass tended to increase (P = 0.07) and body fat mass decreased significantly (P > 0.01). Number of severe hypoglycaemic (< 3 mmol/l) attacks decreased significantly (P < 0.04) and quality of life assessed by validated questionnaires improved significantly in all patients [Psychological and General Well-Being Schedule (PGWBS), P < 0.04; Nottingham Health Profile (NHP), P < 0.05]. Monthly eye photographs revealed no changes in the retina in any patients.

CONCLUSION

GH replacement therapy has a beneficial effect at the dose used. It restores body composition and decreases frequency and severity of hypoglycaemic episodes, thus improving quality of life. Long-term trials are needed to determine the safety of GH replacement therapy in these patients.

The role of growth factors in the development of diabetic retinopathy

Proliferation of retinal blood vessels is one of the most striking features of advanced diabetic retinopathy. This feature has led to the conclusion that the normal balance of growth factors, which usually serves to keep angiogenesis in check, is disturbed in diabetic retinopathy. A considerable amount of work has been performed in the field of angiogenesis within the last decade. Much of this is applicable to diabetic eye disease, but due to the lack of an animal model, few studies have been performed directly on models of diabetic retinopathy. This review examines the literature as it relates to diabetic retinopathy.

Long-term follow-up of patients who underwent yttrium-90 pituitary implantation for treatment of proliferative diabetic retinopathy

Between 1960 and 1976 117 patients underwent pituitary implantation with yttrium-90 (90Y) for treatment of proliferative retinopathy at the Hammersmith Hospital, London. Mean age at operation was 35 +/- 11 years (mean +/- SD), and mean duration of diabetes 18.6 +/- 10.0 years. Mean insulin dosage prior to implant was 67.2 +/- 24 units, falling to 30.4 +/- 14.9 units post-implant. Thirty-two per cent of patients are still living, 60% are deceased and 8% are lost to follow-up. The 5-year survival rate was 82%. Of the causes of death, 21% died of infection, adrenal insufficiency or hypoglycaemia, 12% of renal failure, and 47% of myocardial or cerebral vascular disease. Ophthalmological follow-up was carried out on the 100 patients operated on between 1965 and 1976. The mean age of this group at implant was 35 +/- 10.5 years, and mean duration of diabetes 17.2 +/- 8.7 years. Visual acuity in the better eye at operation was 6/12 or better in 84% of patients, and this percentage remained similar at the time of the 5 and 10 year follow-up. Blindness (6/60 or worse) in both eyes was present in 12% of patients at the time of 5 and 10 year assessments. By 5 years new vessels on the disc had improved from a mean grading of 2.7 +/- 1.6 to 0.8 +/- 1.2 (p less than 0.001), and by 10 years there was no disc neovascularisation in any eye. There was a similar improvement in the grading of hard exudates, microaneurysms and haemorrhages, but there was an increase in fibrous retinitis proliferans.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma somatomedin activity and diabetic retinopathy

Somatomedin activity was measured by a rabbit chondrocyte bioassay in plasma of adult patients with insulin-dependent diabetes of 11-28 years duration. Mean somatomedin activity in patients with background or proliferative retinopathy, assessed by ophthalmoscopy or fluorescein angiography, was 1.42 +/- 0.65 U/ml (n = 20) which was significantly greater than in age- and weight-matched control subjects (1.05 +/- 0.22 U/ml, n = 9). In contrast, somatomedin activity was not raised in patients who had no retinopathy (1.16 +/- 0.33 U/ml, n = 10). Diabetic patients with retinopathy also showed the greatest differences between repeat samples suggesting wider fluctuations in plasma somatomedin levels. Plasma growth hormone and glucose measured either simultaneously with somatomedin or during a 12-24 h profile were not different when diabetics with or without retinopathy were compared. The somatomedins have mitogenic actions in vivo on a variety of connective tissues. The possibility that this may extend to retinal vessels should be further evaluated.

Fate of insulin in the retina: an autoradiographic study

A system for whole-blood perfusion of the bovine eye through the cilioretinal artery was developed and the distribution and binding of 125I-labelled insulin and human growth hormone (HGH) were studied autoradiographically. Sodium fluorescein was used as a tracer to monitor blood retinal barrier integrity, and electron microscopy was used to determine structural preservation after perfusion fixation. With this system, barrier integrity and structural perservation of both the neural retina and the retinal blood vessels were regularly obtained, with perfusion periods of as long as 5 hours. By quantitative light microscopy autoradiography, insulin binding sites were identified on the endothelial cells of retinal capillaries after perfusion with blood containing 125I-insulin. 125I-insulin binding was competitively inhibited by the addition of unlabelled insulin to the perfusing blood. By contrast the low level of binding of HGH to retinal capillaries was nonspecific. Electron microscopy autoradiography revealed 125I-insulin autoradiographic grains lying over the endothelial cell wall, over pinocytotic vesicles, and over the cytoplasm of both endothelial cells and pericytes. This suggests that, after binding to the cell surface, some insulin passes into the cell cytoplasm. However, neither 125I-HGH penetrated as far as the retina in the periods studied.

Reversal of diabetic retinopathy by continuous subcutaneous insulin infusion: a case report

We report the case history of a 20-year-old diabetic girl with long-standing poorly controlled disease who presented with severe retinopathic features and who was treated with continuous subcutaneous insulin infusion (CSII). When first seen she had macular oedema and a visual acuity of 6/18 in her only eye, together with multiple blot haemorrhages and intraretinal microvascular abnormalities. Marked reversal of the retinal lesions occurred within 65 days of initiating SCII and after only 36 days of constant normoglycaemia. Subsequent good blood glucose control on conventional subcutaneous insulin injections has been achieved, and the retinopathy remains quiescent with a visual acuity of 6/5. We suggest that CSII may be a potentially useful method of arresting and reversing early diabetic retinopathy.