Immediate increase of thyroid hormone release during acute stress in rats: effect of biogenic amines rather than that of TSH?

Abstract

An increase of thyroxine (T4; 36% in average) and 3,5,3'-triiodothyronine (T3; 9% in average) levels in plasma was found in rats after 2 min of immobilization stress (IMO), while later (from 5 to 240 min of IMO) the level of both hormones decreased sharply. This increase was prevented by ip injection of phenoxybenzamine (4 or 16 mg kg\ m=-\ 1), prazosin (2.5 mg kg\ m=-\ 1), yohimbin (4 or 16 mg kg\ m=-\ 1) and fluoxetine (10 mg kg\ m=-\ 1) at 60 min before IMO, but similar injections of phentolamine (4 or 16 mg kg\m=-\1), tolazoline (4 or 16 mg kg\ m=-\ 1), methysergide (10 mg kg\m=-\1), cyproheptadine (10 mg kg\ m=-\ 1) as well as of lower doses of prazosin (0.6 or 1.2 mg kg\ m=-\ 1) did not show such an effect. The level of TSH was increased after 2 min IMO too, but this was considered to be a separate phenomenon from the increase of T4 and T3, since in several groups injected with some of the above drugs the level of TSH was decreased together with increased levels of T4 and T3. It is suggested that the acute release of thyroid hormone might be due to the effect of biogenic amines which may be blocked by some alpha-adrenergic blocking agents. Since neither adrenalectomy nor adrenal-medullectomy prevented such a release, it may be concluded that circulating catecholamines of adrenal origin did not play any role in this process. The possibility of participation of intrathyroidal sympathetic nerve endings was also repeatedly tested after pharmacological sympathectomy achieved by a long-term administration of guanethidine, but data obtained to date have been inconsistent.

Interpreting Stress Responses during Routine Toxicity Studies

“…Acute stress is associated with transiently increased T4 secretion and increased circulating T4 concentrations within a few minutes of the stressor (Langer et al 1983). The mechanism is unknown, but it may be due to catecholamine release or sympathetic innervations of the thyroid gland.…”

Stress and thyroid gland

“…При остром психогенном стрессе [12], после 2-минутной иммобилизации у крыс отмечено повышение в крови содержания Т 4 и Т 3 , при более продолжительном воздействии (5-240 минут) уровень тиреоидных гормонов [13] или только Т 3 [14] снижается. Наряду со снижением содержания Т 3 обнаружено повышение в сыворотке концентрации rТ 3 , отсутствие изменения уровня Т 4 на фоне снижения концентрации тиреотропного гормона (ТТГ) [15].…”

The Effects of Acute and Chronic Immobilization Stress and Aloe vera Extract on Serum Levels of TSH, T3 and T4 in Male Rats

“…Immobilization is a kind of physiological stress which has two types of acute and chronic in different organisms and can have different effects on physiology of animals, including their growth, physiological function of hypothalamus, pituitary, adrenal and thyroid glands, particularly (1)(2)(3)(4)(5)(6)(7)(8). On the other hand, thyroid is one of the most important endocrine glands which regulate various functions in the body (9).…”