Thyroid funtion, plasma insulin, glucose and ketones and in vitro hepatic gluconeogenesis in rats under chronic low iodine intake.

Abstract

Weaning female rats were fed for 1.3-14 months with a low iodine diet (LID) and compared with age matched controls on KI03 supplemented LID (C). At sacrifice the LID rats had large goitres, low plasma PBI and thyroidal 1271 content, a rapid thyroidal-1311 (*I) turnover and increased '"MIT/''DIT and ''T3/''T4 ratios. Body weights were slightly higher in LID and pituitary growth hormone like protein bands were the same in both groups. There were no differences between LID and C, whether fed or fasted for 48 h with regard to plasma insulin, glucose and ketone bodies. In vitro disposition of trace or 10-2 M alanine-U-14C by liver slices were the same as measured by I4C incorporation into CO2, glucose and lactic acid. The response of these parameters to fasting was normal: plasma insulin and glucose decreased and ketone bodies and in vitro gluconeogenesis increased. The lack of alteration in the intermediary metabolism of rats, sufficiently iodine deficient to develop goitre, has been interpreted as indicating either that: 1) thyroid hormones have no direct effect on the parameters of intermediary metabolism studied, or 2) there is enough hormone available to the tissues to keep a normal metabolism but not to suppress TSH secretion, thus suggesting different sensitivities to the hormone.