Platelet serotonin concentration and monoamine oxidase activity in hypothyroid patients.
OBJECTIVE
The relationship between the hypothalamic-pituitary-thyroid (HPT) axis and the serotonergic (5-hydroxytryptamine, 5-HT) system is not clear. The aim of the study was to determine platelet biochemical markers (5-HT concentration and monoamine oxidase B, MAO-B, activity) in hypothyroid patients.


METHODS
The study included 25 medication-free female hypothyroid patients in postoperative follow-up after total thyroidectomy due to papillary thyroid carcinoma, who had not been treated with synthetic thyroxine (T(4)) for 4 weeks, and 44 age-matched euthyroid healthy women. The platelet 5-HT concentration, platelet MAO-B activity, total T(4) and thyroid-stimulating hormone (TSH) levels were determined using spectrofluorimetric methods, radioimmunoassay and fluoroimmunoassay, respectively.


RESULTS
Hypothyroid patients had significantly higher TSH, significantly lower T(4) levels and platelet 5-HT concentrations, and unchanged platelet MAO-B activity than healthy subjects. A positive correlation was found between the 5-HT concentration and platelet MAO-B activity, and between the platelet MAO-B activity and T(4) in control subjects.


CONCLUSIONS
Reduced platelet 5-HT concentrations in hypothyroid patients suggests a complex interaction between the 5-HT system and HPT axis activity, which could be related to the frequent occurrence of depressive symptoms in hypothyroid patients. The determination of platelet 5-HT concentrations should be considered a diagnostic tool for the evaluation of depressive symptoms in hypothyroid patients during the hormone withdrawal procedure.
Stipcevic
Tamara
T
Division of Molecular Medicine, Rudjer Boskovic Institute, Zagreb, Croatia. tamara@irb.hr
Kusacic-Kuna
Sanja
S
Dezeljin
Martina
M
Dodig
Damir
D
Korsic
Mirko
M
Pivac
Nela
N
Muck-Seler
Dorotea
D
D000328:Adult; D000368:Aged; D001792:Blood Platelets / Q000378:metabolism*; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000201:enzymology*; D008875:Middle Aged; D008995:Monoamine Oxidase / Q000097:blood*; D012701:Serotonin / Q000097:blood*; D013375:Substance Withdrawal Syndrome / Q000097:blood; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood
D012701:Serotonin; D013972:Thyrotropin; D008995:Monoamine Oxidase; D013974:Thyroxine