Hypokalaemia during insulin-induced hypoglycaemia in hypopituitary adults with and without growth hormone deficiency

Abstract

OBJECTIVE: We have investigated plasma potassium changes during insulin- induced hypoglycaemia (IIH) in adult patients with growth hormone deficiency (GHD) who have low total body potassium and may also have a vulnerable myocardium due to an increased prevalence of atherosclerosis. DESIGN: Hypoglycaemia was induced through the administration of intravenous soluble insulin (0.1 U/Kg, IV). SUBJECTS: 23 consecutive adult patients undergoing routine biochemical evaluation for hypopituitarism. MEASUREMENTS: GH, cortisol glucose, sodium and potassium levels were measured at 0, 30, 60, 90 and 120 min after insulin administration. Pituitary function was also assessed through measurement of TSH, thyroid hormones, LH/FSH, testosterone and 17-oestradiol. IGF-I concentrations were also analysed. RESULTS: All patients achieved adequate hypoglycaemia (nadir glucose<2 mmol/l). 15 patients had GHD (peak GH < 10 mu/l) either in isolation or as part of a spectrum of pituitary hormone deficiencies. The remaining 8 patients had normal pituitary function. Plasma potassium concentrations (mean ± SEM) fell from 3.8 ± 0.3 mmol/l (normals) and 3.8 ± 0.2 mmol/l (GHDs) to nadir concentrations of 3.0 ± 0.2 mmol/l and 3.1 ± 0.3 mmol/l, respectively (P<0.005). Overt hypokalaemia (<3.5 mmol/l) occurred in 13/15 GHDs and all normals. There were no significant differences between the groups. CONCLUSIONS: Insulin-induced hypoglycaemia causes similar degrees of significant hypokalaemia in patients with normal pituitary function and in those with GH deficiency, either alone or in combination with other pituitary hormone deficiencies. Therefore, insulin-induced hypoglycaemia does not appear to be associated with any greater risk of hypokalaemia in hypopituitary adults with GHD compared to those with normal anterior pituitary function.