Evaluation of the Nocturnal Serum Thyrotropin (TSH) Surge, as Assessed by TSH Ultrasensitive Assay, in Patients Receiving Long Terml-Thyroxine Suppression Therapy and in Patients with Various Thyroid Disorders*

Dec 1, 1987The Journal of clinical endocrinology and metabolism

Nighttime rise in thyroid-stimulating hormone measured by sensitive test in patients on long-term thyroid hormone therapy and with different thyroid conditions

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Abstract

Of the 30 patients receiving long term L-T4 suppression therapy, 28 had undetectable serum TSH both during the night and in the morning.

Circadian variations in serum TSH concentrations were noted, with higher levels occurring in the late evening or early morning.
Normal subjects and patients receiving L-T4 replacement therapy exhibited higher serum TSH values at night compared to the morning.
Patients with hypothyroidism showed exaggerated TSH responses to TRH, while those with central hypothyroidism had no nocturnal surge or response to TRH.
All hyperthyroid patients had undetectable serum TSH levels both day and night, with no response to TRH.
Among patients with nontoxic goiter, some had detectable serum TSH in the morning with higher night values, while others had undetectable levels and abnormal TRH responses.

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Circadian variations of serum 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 undetectable 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 untreated or inadequately treated with 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 normal subjects a major TSH surge occurred between 2300-0100 h, with other minor peaks, and the same pattern was found in two 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. less than 0.07 mU/L). In the remaining patients blood was drawn at hourly intervals between 2300-0200 h and on the next morning before (0830-0900 h) and 30 min after iv TRH administration. In normal subjects, in patients receiving L-T4 replacement therapy, and in hypothyroid patients, serum TSH values at night were higher 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 to TRH; the remainder had undetectable serum TSH both at night and in the morning, and subnormal or absent TSH responses to TRH. All 5 patients with a functioning thyroid adenoma had undetectable serum TSH levels in the morning and during the night, and subnormal or absent TSH responses to TRH. Of the 30 patients receiving long term (greater than 6 months) L-T4 suppression therapy, 28 had undetectable serum TSH both during the night and in the morning and unresponsiveness to TRH.(ABSTRACT TRUNCATED AT 400 WORDS)

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Evaluation of the Nocturnal Serum Thyrotropin (TSH) Surge, as Assessed by TSH Ultrasensitive Assay, in Patients Receiving Long Terml-Thyroxine Suppression Therapy and in Patients with Various Thyroid Disorders*

Abstract

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