Gillet C, Corvilain J, Matte-Hiriart J, Willems D, Bergmann P
Clinic of Endocrinology and Metabolism, Hôpital Universitaire Brugmann, Free University of Brussels, Belgium.
J Clin Endocrinol Metab. 1990 Aug;71(2):516-9. doi: 10.1210/jcem-71-2-516.
In chronic hypercalcemia, basal TSH has been found to be low, with normal serum circulating concentrations of T3 and T4. This observation suggested a potentiation by hypercalcemia of the thyroid secretory response to TSH. The present study was undertaken to assess the possible influence of hypercalcemia on the T3 secretory response to TSH. Since T3 secretion was studied after stimulation of endogenous TSH by TRH, it was first necessary to find a protocol enabling us to study the effect of calcium on T3 release without affecting TSH secretion. Eighteen subjects underwent two TRH tests, with and without simultaneous calcium infusion, at 2-week interval and in a randomized order. In group A (five subjects) calcium infusion started 1 min after TRH, in group B (five subjects) 10 min after TRH, and in group C (eight subjects) 20 min after TRH. In groups A and B, TSH secretion was markedly blunted by hypercalcemia. In contrast, when calcium infusion was started 20 min after TRH (group C), the TSH secretion profile was no longer different from that in the control study. However, in this situation the increments of T3 and free T3 120 and 180 min after TRH were significantly higher when the subjects were rendered hypercalcemic than in the control study. These findings suggest that calcium might act at two different levels, to enhance the thyroid secretory response to TSH and decrease TSH secretion by acting directly on the pituitary gland. Both effects would produce the association of low serum TSH and normal levels of T3 and T4 observed in chronic hypercalcemia.
在慢性高钙血症中，已发现基础促甲状腺激素（TSH）水平较低，而血清中三碘甲状腺原氨酸（T3）和甲状腺素（T4）的循环浓度正常。这一观察结果提示高钙血症可增强甲状腺对TSH的分泌反应。本研究旨在评估高钙血症对TSH刺激后T3分泌反应的可能影响。由于T3分泌是在促甲状腺激素释放激素（TRH）刺激内源性TSH后进行研究的，因此首先有必要找到一种方案，使我们能够研究钙对T3释放的影响，而不影响TSH分泌。18名受试者每隔2周按随机顺序接受两次TRH试验，一次同时输注钙，一次不输注。A组（5名受试者）在TRH后1分钟开始输注钙，B组（5名受试者）在TRH后10分钟开始，C组（8名受试者）在TRH后20分钟开始。在A组和B组中，高钙血症使TSH分泌明显减弱。相反，当在TRH后20分钟开始输注钙时（C组），TSH分泌情况与对照研究不再有差异。然而，在这种情况下，当受试者处于高钙血症状态时，TRH后120分钟和180分钟时T3和游离T3的增量显著高于对照研究。这些发现表明，钙可能在两个不同水平起作用，通过直接作用于垂体来增强甲状腺对TSH的分泌反应并降低TSH分泌。这两种作用将导致在慢性高钙血症中观察到的低血清TSH与正常T3和T4水平并存的现象。
