engleski

Peripheral serotonergic markers after thyroidectomy: the effect of antihypertensive medications

Background: Previous studies with thyroid dysfunction have shown some evidence that hypothyroid status could be associated with altered serotonin (5-HT) responsiveness. Additionally hypothyroidism is frequently associated with arterial hypertension. Platelet serotonin (5-HT) levels and platelet monoamino oxidase (MAO B) activity might be used as limited peripheral markers of the central 5-HT system. Objective: The aim of the study was to determine a) the relationship between thyroid state and peripheral serotonergic markers (platelet 5-HT and MAO B) and b) the effect of antihypertensive drugs (adrenergic blocking agents) on platelet 5-HT levels and MAO B activity in hypothyroid patients and euthyroid control subjects. Material and methods: The study included 41 hypothyroid patients in postoperative evaluation after total thyroidectomy from papillary thyroid carcinoma and 67 age and sex matched euthyroid healthy controls. Before 131I whole body scanning and measurement of serum thyroglobulin, patients were 6 weeks free of euthyrox (levothyroxine-synthetic thyroxine) and other medications, with the exception of antihypertensive therapy. Sixteen patients and 19 control subjects were taking different antihypertensives including alpha 1 and beta adrenoceptors blockers in combination with angiotensin converting enzyme II antagonists and calcium channel blockers. All subjects were free of concomitant psychiatric and endocrine illnesses. Blood sampling was done in the morning in all subjects after an overnight fasting, prior to radiological (patients) and medical examinations. Platelet 5-HT and MAO B activity were determined using spectrofluorimetric methods and total thyroxin (T4) and thyroid stimulating hormone (TSH) levels using commercially available radioimmunoassay and immunometric kits. Results: As expected T4 levels were significantly (p<0.05) decreased and TSH levels increased in patients as compared to hormone values in control subjects. Platelet 5-HT values were significantly (p<0.001) lower in hypothyroid patients compared to healthy controls. There was no significant difference in MAO B activity between patients and control subjects. A positive correlation between 5-HT levels and MAO B activity was found but only in the control subjects. A significantly lower (p=0, 025) 5-HT levels were observed in the subgroup of control participants taking antihypertensive medications compared to those without medications. Similar platelet 5-HT values were found in both patients with or without antihypertensive medication. Antihypertensive therapy did not influence platelet MAO B activity in patients or control subjects. Conclusion: Our results show a positive relationship between severe hypothyroidism and decrease in peripheral 5-HT concentration. The findings suggest that the pharmacological features of alpha 1 and beta adrenoceptor antagonist could be relevant to the psychopharmacotherapy. Further studies are needed to elucidate the interaction between the thyroid function, serotonergic system and antihypertensive medications in healthy controls and patients with mental disorders.

thyroid function; serotonergic system; antihypertensive medications; healthy controls; patients with mental disorders

Periodicum Biologorum. Supplement (ISSN 0353-9164) 109 (2007) Suppl. 2