Glucoregulatory function of glucagon in hypo-, eu- and hyperthyroid miniature pigs

Abstract

The glucoregulatory function of glucagon was investigated in hypo-, eu- and hyperthyroid miniature pigs. Infusion glucagon, (3 ng x kg body weight-1.min-1) transiently increased blood glucose (p less than 0.01) and hepatic glucose production (p less than 0.01) in euthyroidism, but was without effect in hyperthyroidism. Infusing glucagon plus somatostatin (2 ng x kg body weight-1.min-1 and 0.2 microgram x kg body weight-1.min-1) transiently increased blood glucose (delta 3.0 to 4.3 mmol/l) and hepatic glucose production (delta 3.3 to 7.7 mumol x kg body weight-1.min-1) in all thyroid states, the effect was less pronounced in hyperthyroid pigs. By contrast, hypoglucagonaemia (74 to 107 pg/ml) at basal insulin (28 to 35 microU/ml) provoked hypoglycaemia (1.4 to 2.2 mmol/l) and a fall in glucose production (delta 4.7 to 8.3 mumol x kg body weight-1.min-1), which was independent of the thyroid state; the effect was most pronounced in hyperthyroidism (p less than 0.01). Hepatic glycogen content, arterial gluconeogenic precursor concentrations as well as the glycaemic response (delta 0.60 mmol/l) to alanine infusion (23 mumol x kg body weight-1.min-1) were all unaffected by hyperthyroidism. We conclude that moderate experimental hyperthyroidism reduces glucagon action due to reduced glycogen mobilisation. This may in part result from increased insulin sensitivity.

Glucoregulatory Function of Thyroid Hormones: Evidence for an Insulin-Independent Effect

“…However, infusing somatostatin plus basal amounts of glucagon (i.e. keeping the arterial glucagon concentration nearlyc onstant) results in a less pronounced increase in Ra in hyperthyroidisni (Müller et al, 1988). Therefore, there is evidence that hyperthyroidism decreases hepatic glucagon sensitivity, which is in agreement with previous data in man ).…”

“…Regarding glucagon action the data are confusing too: arterial glucagon is elevated or unchanged in hyperthyroidism (Müller et. al., 1983a;Bratusch-Marrain et al, 1984) and thyroid hormones are said to induce increased (Guttlei et al, 1977;Müller et al, 1988;or tiecreased (Muller et al, 1988; hepatic glucagon sensitivity. With respect to the role of hyperglycemia, to our knowledge no data have been published un the effect of glucose by itself on glucose turnover in hyperthyroidi.sm.…”

Insulin Action in Adipose Tissue and Muscle in Hypothyroidism

“…Hepatic glucose production is decreased (3,4) or unchanged (5) in hypothyroidism, but there is little information on the effects of insulin in peripheral tissues and, in particular, in vivo.…”

The Importance of HbA1c Control in Patients with Subclinical Hypothyroidism

“…It is a part of the brain that produces TRH (thyroid releasing hormone). TRH stimulates the pituitary gland to secrete TSH (14, 15, 16). …”