Bellastella A, Sinisi A A, Criscuolo T, De Bellis A, Carella C, Iorio S, Sinisi A M, Parlato F, Venditto T, Pisano G
Institute of Endocrinology, Second University of Naples, Italy.
Clin Endocrinol (Oxf). 1995 Dec;43(6):707-11. doi: 10.1111/j.1365-2265.1995.tb00539.x.
Increased levels of free thyroid hormones have been previously described in prepubertal blind subjects and have been thought to be a consequence of a partial target organ refractoriness due to the early and prolonged lack of light perception. The aim of this study was to clarify whether this abnormality is permanent or transient and the interrelationships between melatonin and thyroid hormone secretion.
Total and free thyroid hormones, TSH, thyroxine-binding globulin (TBG), reverse triiodothyronine (rT3) and melatonin were measured in plasma samples obtained at 0800 h (two hours after lights-on) in a group of 11 totally (group 1) and 16 partially (group 2) blind adult patients and in 10 age-matched healthy subjects.
Both totally and partially blind patients showed melatonin levels higher than in controls (330 +/- 106 pmol/l, group 1 and 361 +/- 159 pmol/l, group 2, respectively; controls: 53 +/- 12 pmol/l, P < 0.001 vs both groups), but fT4, fT3, T4, T3 TSH, rT3 and TBG concentrations showed no significant differences from controls.
A possible resetting of pituitary-thyroid axis regulation can occur in blindness after puberty; variations of melatonin secretion could play a role in this. The inhibitory effect of melatonin on thyroid gland function found in animals does not seem to occur in humans. Elevated melatonin levels, both in patients with total blindness and in those with light perception only, suggest that more complex mechanisms other than light signalling are involved in the changes of melatonin secretion in blindness.
先前已描述青春期前失明受试者的游离甲状腺激素水平升高，并且认为这是由于早期和长期缺乏光感知导致部分靶器官难治性的结果。本研究的目的是阐明这种异常是永久性的还是短暂性的，以及褪黑素与甲状腺激素分泌之间的相互关系。
在上午08:00（开灯后两小时）采集的血浆样本中，对11名完全失明（第1组）和16名部分失明（第2组）的成年患者以及10名年龄匹配的健康受试者测量总甲状腺激素和游离甲状腺激素、促甲状腺激素（TSH）、甲状腺素结合球蛋白（TBG）、反三碘甲状腺原氨酸（rT3）和褪黑素。
完全失明和部分失明患者的褪黑素水平均高于对照组（第1组为330±106 pmol/l，第2组为361±159 pmol/l；对照组为53±12 pmol/l，与两组相比P<0.001），但游离甲状腺素（fT4）、游离三碘甲状腺原氨酸（fT3）、甲状腺素（T4）、三碘甲状腺原氨酸（T3）、TSH、rT3和TBG浓度与对照组无显著差异。
青春期后失明可能会发生垂体 - 甲状腺轴调节的重新设定；褪黑素分泌的变化可能在此过程中起作用。动物中发现的褪黑素对甲状腺功能的抑制作用在人类中似乎未发生。完全失明患者和仅具有光感知患者的褪黑素水平升高表明，除光信号外，更复杂的机制参与了失明时褪黑素分泌的变化。
