Comparative study of imipramine, amitriptyline and their desmethyl analogues in the hypothyroid rat

The effects of thyroid state on beta-adrenergic and serotonergic receptors in rat brain

“…In a study of the interactions of DMI and T 3 , Atterwill et al (1986) noted that a single dose of T 3 (100 µ.g/kg) on day 1 slightly decelerated the rate of betaadrenergic receptor down-regulation induced by daily injections of DMI (5 mg/kg) for 14 days. It is interesting that DMI was effective in down-regulating beta-adrenergic receptors of thyroidectomized rats; it has been suggested, though only by anecdotal evidence, that TCAs are not as effective in hypothyroid patients (Avni et al, 1967). If down-regulation occurs in hypothyroid depressed patients, even as these patients show a poor or null antidepressant response, the down-regulation cannot be a sufficient explanation for the usual therapeutic action ofTCAs.…”

Thyroid hormones in the treatment of affective disorders

“…Depression is significantly more frequent in hypothyroid than in hyperthyroid patients (2). In addition TCA's seem to be less effective in depressed patients suffering from hypothyroidism (14). However, direct evidence contradicts this hypothesis.…”

“…Intrinsic mobilization, or the addition of small doses of thyroid hormones, could shift the HPT axis to such an optimal state (89). If we accept that hypothyroidism may decrease the efficacy of TCA's (14), optimizing the H P T axis state may promote their action in the treatment of depression (89). While some optimal level of thyroid activity seems necessary for an adequate response t o TCA's (3) exceeding that level does not seem helpful, as evidenced by reports (89) that the depression of some frankly hyperthyroid patients does not respond well to antidepressant therapy.…”

“…Endogenous (major) depression shares many clinical symptoms with hypothyroidism, including anergia, fatigue, sleep, appetite and weight changes, and constipation (12,13). It has also been demonstrated that tricyclic antidepressants may be less effective in the presence of hypothyroidism (14).…”