Fatty acid composition of serum lipid fractions in thyroid disease

Fatty acid composition in plasma and platelet phospholipid in hypothyroid patients before and after 1-thyroxine substitution

The relative concentration of fatty acids in plasma and platelet phospholipids (phosphatidylcholine) was determined in 11 patients with overt hypothyroidism (S-TSH greater than 80 mU/l) before and after 1-thyroxine substitution therapy. During therapy, the linoleic (C18:2) acid content decreased (p less than 0.01) whereas longer and more desaturated fatty acids, including arachidonic (C20:4) acid, increased (p less than 0.01) in plasma phospholipids. Also, oleic (C18:1) acid decreased (p less than 0.01) while the major saturated fatty acids, palmitic (C16:0) and stearic (C18:0) acids, were stable. In platelet membrane phospholipids, a similar reciprocal change in the relative content of linoleic (C18:2) and arachidonic (C20:4) acids, respectively, occurred. In plasma, these changes in linoleic and arachidonic acids were found to be inversely correlated (r = 0.56, p less than 0.05). The change in the linoleic acid content in plasma was also correlated to that in platelets (r = 0.64, p less than 0.05). Thus, we have found that thyroid hormones positively influence the conversion of linoleic acid to longer and more polyunsaturated fatty acids in a way that affects fatty acid composition not only in plasma but also in platelet membrane phospholipids.

Changes in fatty acid profiles of plasma, erythrocytes and polymorphonuclear leukocytes in induced hypothyroidism in man: indirect evidence for altered delta 6 desaturase activity

Thirteen patients who were athyreotic as a consequence of ablation treatment for well-differentiated thyroid cancer were studied during triiodothyronine supplementation, and subsequently at the end of a two weeks withdrawal of this medication. Serum and plasma lipid concentrations, erythrocyte cholesterol content and plasma and erythrocyte total fatty acid patterns were measured. In addition, total fatty acid profiles of polymorphonuclear leukocytes of eight patients and scanning electron microscopic studies of erythrocytes of nine patients were made. We observed an increase of the serum concentrations of total and unesterified cholesterol and phospholipids in all patients. Except for two, all patients showed an increase in the serum triglyceride concentration. The relative amounts of 18:2c,omega 6 rose and those of 20:3c,omega 6 fell in all studied compartments. In addition, the relative amounts of all other omega 6 fatty acids, 22:6c,omega 3, 20:3c,omega 9, 16:0, 18:0, and total saturated fatty acids decreased in plasma, whereas the levels of all monounsaturated fatty acids increased in the erythrocytes. The level of 20:3c,omega 9 rose in the erythrocytes and the 20:3c,omega 9/20:4c,omega 6 ratio rose in the polymorphonuclear leukocytes. The erythrocyte total fatty acids and cholesterol content and their ratio did not change, nor was any alteration seen in the red cell morphology by scanning electron microscopy. This study reveals that the induction of hypothyroidism in man changes fatty acid patterns of plasma, erythrocytes and polymorphonuclear leukocytes. The nature of these alterations suggests especially a disturbance in the delta 6 desaturase activity. The data point to the possibility of a derangement of eicosanoid synthesis in hypothyroidism.

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.

A rapid quantitative determination of triglycerides by means of thin-layer chromatography

A quantitative chromatographic method for determining triglycerides in serum is described. The serum is applied directly to a thin-layer plate and after partition with one developing solvent the fractions are charred with 10% sulphuric acid. Charring takes 20 minutes. The concentration of triglycerides is measured against a triolein standard, which in itself is corrected for having too many double bonds by scanning the charring of the triglyceride fraction with a "flying spot"-scanner or a slitscanner. The results are compared with other methods of determination.