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KMID : 0377819880080080969
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Diagnosis and Treatment
1988 Volume.8 No. 8 p.969 ~ p.976
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EVALUATION OF THE NOCTURNAL SERUM THYROTROPIN(TSH) SURGE AS ASSESSED BY THS ULTRASENSITIVE ASSAY IN PATIENTS RECEIVING LONG TERM L-THYROXINE SUPPRESSION THERAPY AND IN PATIENTS WITH VARIOUS THYROID DISORDERS
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Abstract
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Circadian variations of serurn TSH concentrations have been reported, with higher values occurring in the late evening or early morning. In patients receiving long term L-T₄, suppression therapy, it may be important to achieve; suppression of TSH secretion throughout the day. To investigate whether undetectable serum TSH values in the morning are associated with undetectabel serum TSH levels at night, serum TSH concentrations were measured by an ultrasensitive immunoradiometric assay in 16 normal subjects, 20 hyperthyroid patients, 10 patients with primary hypothyroidism (either untreasted or inadequately treated ith L-T₄), 1 patient with central hypothyroidism,10 patients with nontoxic nodular goiter, 5 patients with functioning thyroid adenoma, 20 patients receiving L - T₄ replacement therapy, and 30 patients receiving L-T₄ suppression. In 6 subjects blood. was drawn at hourly intervals for 24 h: in 2 nominal subjects a major TSH surge occurred between 2300-0100 h, with other minor peasks, and the same pattern was found in two patients receiving L-T₄ replacement, whereas in 2 patients receiving L-T₄ replacement, whereas, in 2 patients receiving L-T₄ suppression, serum TSH was constantly below the limit of detection of the assay (i,e＜0.07 mU / L ). In the remaining patients blood was drawn at hourly intervals between 2300-0200 and on the next morning before90-830-0900 h) and 30 min sfter iv TRH administration. In normal subjects, inpatients receiving L-T₄ replacement therapy, and in hypothyroid patients, serum TSH values; at night were highter than in the morning, with normal responses to TRH in the first 2 groups and exaggerated responses in the latter., The patient with central hypothyroidism had no nocturnal TSH surge and no TSH response to TRH. In all hyperthyroid patients, serum TSH was undetectable both at night and during the day, and none had a serum TSH response to TRH. Among patients with nontoxic goiter, 7 had detectable serum TSH in the morning, with higher values at night, and a normal response toTRH; the remainder had undetectable serum TSH both at night and in the morning, and subnormal or abwsent TSH responses to TRH. All 5 patients with a functioning thyroid adenoma had undetectabel serum TSH levels in the momig and during to night, dand subnormal or absent TSH responses to TRH, of the 30 patients receiving long tetm(＞6 months) L-T₄ suppression therapy, 28 had undetectabel serum TSH both during the night and in the morning and unresponsiveness to TRH.
In conclusion, undetectable basal serum TSH levels in the morning are associated with lack of a physiological TSH surge at night(and, in general, with unresponsiveness to TRH administration). Conversely, detecable, although subnormal, serum TSH values in the momign in patients receiving L-T₄ therapy replect incomplete suppression of ednogenous TSH secretion, as indicated by the persistence of a TSH surge during the night. (J Clin Endocrinol Metab 65 : 1265, 1987).
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KEYWORD
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