Thyrotoxicosis is a common endocrine condition that may be secondary to a number of underlying processes. Thyroid storm (also known as thyroid or thyrotoxic crisis) represents the severe end of the spectrum of thyrotoxicosis and is characterized by compromised organ function. Whilst rare in the modern era, the mortality rate remains high, and prompt consideration of this endocrine emergency, with specific treatments, can improve outcomes.

We evaluated the effect of aging on fat and carbohydrate metabolism during moderate intensity exercise. Glycerol, free fatty acid (FFA), and glucose rate of appearance (Ra) in plasma and substrate oxidation were determined during 60 min of cycle ergometer exercise in six elderly (73 +/- 2 yr) and six young adults (26 +/- 2 yr) matched by gender and lean body mass. The elderly group was studied during exercise performed at 56 +/- 3% of maximum oxygen uptake, whereas the young adults were studied during exercise performed at the same absolute and at a similar relative intensity as the elderly subjects. Mean fat oxidation during exercise was 25-35% lower in the elderly subjects than in the young adults exercising at either the same absolute or similar relative intensities (P < 0.05). Mean carbohydrate oxidation in the elderly group was 35% higher than the young adults exercising at the same absolute intensity (P < 0.001) but 40% lower than the young adults exercising at the same relative intensity (P < 0.001). Average FFA Ra in the elderly subjects was 85% higher than in the young adults exercising at the same absolute intensity (P < 0.05) but 35% lower than the young adults exercising at a similar relative intensity (P < 0.05). We conclude that fat oxidation is decreased while carbohydrate oxidation is increased during moderate intensity exercise in elderly men and women. The shift in substrate oxidation was caused by age-related changes in skeletal muscle respiratory capacity because lipolytic rates and FFA availability were not rate limiting in the older subjects.

Stable isotope tracers and indirect calorimetry were used to evaluate the progressive alterations in lipid and glucose metabolism after 12, 18, 24, 30, 42, 54, and 72 h of fasting in six healthy male volunteers. The rates of appearance (Ra) of glycerol and palmitic acid in plasma doubled from 2.08 +/- 0.22 and 1.63 +/- 0.20 mumol.kg-1 x min-1, respectively, after 12 h to 4.36 +/- 0.36 and 3.26 +/- 0.40 mumol.kg-1 x min-1, respectively, after 72 h of fasting (P < 0.01). Of the total increase in lipid kinetics, 60% occurred between 12 and 24 h of fasting; the greatest interval change occurred between 18 and 24 h of fasting. Glucose Ra and plasma concentration decreased by approximately 25% between 12 h (11.0 +/- 0.4 mumol.kg-1 x min-1 and 5.58 +/- 0.08 mmol/l, respectively) and 72 h (8.3 +/- 0.3 mumol.kg-1 x min-1 and 4.14 +/- 0.10 mmol/l, respectively) of fasting (P < 0.01), but no statistically significant changes occurred between 18 and 24 h of fasting. Plasma insulin decreased by approximately 50% between 12 h (64.6 +/- 12.9 pmol/l) and 72 h (30.1 +/- 7.9 pmol/l) of fasting (P < 0.001). Of the total decline in plasma insulin, 70% occurred within the first 24 h of fasting. These results demonstrate that the mobilization of adipose tissue triglycerides increases markedly between 18 and 24 h of fasting in young adult men. The early alterations in lipid metabolism are associated with a decline in circulating insulin but do not seem to be regulated by changes in glucose kinetics or plasma glucose concentrations.

No abstract