Background: Fluoxetine or Prozac is a serotonin reuptake inhibitor (SSRI). Considering the importance of this drug for the treatment of neurological disorder, such as anorexia and depression its side effects on the endocrine axis of body are of significance. Hence, the present study was conducted to evaluate the effects of fluoxetine on cortisol and thyroid hormone levels and body weight in male rates.

Materials and Methods: In this experimental study, 30 adult male rats (230±20 gr BW) were randomly divided into 3 equal groups: sham, control and treatment. Rats in the control group were kept in normal conditions in animal house, whereas treatment and sham groups were, respectively, injected 32 mg/kg BW of fluoxetine and 0.9 ml of normal saline (i.p) for 35 days. During this time, body weight of all animal was measured and after 35 days, blood was collected by heart puncture and separation of serums to evaluate T3, T4, fT3, fT4, and cortisol hormones through RIA method. The results were statisticaly evaluated by one-way ANOVA test.

Results: Taking fluoxetine for 35 days significantly decreased the level (p&le0.05) in serum concentrations of Ft3, fT4, T4 and cortisol hormones compared to the control and sham groups. However, no significant differences were observed in the serum concentration of T3 hormone in treatment group compared to the the control group. The drug also caused a significant decrease in the average weight of rats in the treatment group compared to the control group (p&le 0.05).

Conclusion: By affecting the activity of different levels of hypothalamus-pituitary-adrenal hormones axis, fluoxetin decreases the level of cortisol hormones. It also reduces the activity of the thyroid gland this is probably due to the increased prolactin secretion through inhibiting TRH secretion and reducing the production of TSH and thyroid hormones