Alterations of protein metabolism in myxedema

Atrophy of the zona fasciculata in the adrenal cortex of thyroparathyroidectomized rats: a quantitative study

Atrophy of the adrenal gland induced by thyroparathyroidectomy (TPX) is attributable primarily to narrowing of the zona fasciculata. But absolute volumes of the adrenal gland and zona fasciculata, not the zona glomerulosa and zona reticularis, were decreased significantly 7 weeks after TPX. Changes consistent with atrophy were also seen in the zona fasciculata by electron microscopy. A slight decrease in volume of cytoplasm in cells of the zona fasciculata was evident 2 weeks after TPX as shown by quantitative stereological techniques. Seven weeks after TPX, there was a significant decrease in average cytoplasmic volume as well as mitochondrial volume and surface density of mitochondrial membranes. A decrease in total volume of the zona fasciculata, as well as volume per cell of mitochondria, correlates directly with decreased production of corticosterone in response to stress in TPX rats. Parathyroidectomy (PX) had no effect on the volume of the adrenal gland, on the volume of the individual cortical zones, or on the volume per cell of cytoplasm or mitochondria; these observations indicate that changes in TPX rats are due primarily to ablation of the thyroid gland.

Effect of thyroparathyroidectomy (TPX) on the zona reticularis: a quantitative ultrastructural study

Atrophy of zona reticularis cells was observed two weeks after surgical thyroparathyroidectomy (TPX). Quantitative morphological techniques for electron microscopy showed significant decreases in the volume of cytoplasm, nucleus, mitochondria, smooth endoplasmic reticulum and lipid droplets in the zona reticularis of TPX rats. In addition, many mitochnodria contained lipid droplets, some of which occupied virtually the entire matrix of mitochondria. The volume per cell of mitochondria with these inclusions increased significantly after TPX. The lipid droplets may well arise from cytoplasmic droplets by increased transport or reduced metabolism of cholesterol, or by direct incorporation of droplets into the mitochondrial matrix. The serum corticosterone level of TPX rats sacrificed under quiescent conditions did not differ significantly from that of controls. Hypothyroidism induced a significant increase in the volume of peroxisomes per cell in TPX animals which may be related to changes in lipid metabolism or transport.

Haemostatic and lipid abnormalities in hypothyroidism

10 patients with hypothyroidism were examined before and 3 months after initiation of thyroxin treatment. All patients had high levels of plasma total cholesterol and total phospholipids, and 5 had an additional hypertriglyceridaemia. 1 patient had a prolonged primary bleeding time and all had a prolonged activated partial thromboplastin time and recalcification time in plasma. Platelet factor 3 activity in platelet rich plasma was reduced and total phospholipid and protein concentration in platelets were low. No significant correlation could be estiblished between the observed lipid, protein and haemostatic parameters, and it is suggested that they represent independent phenomena. All abnormalities were corrected by thyroxin replacement.