Circadian and pulsatile TSH secretion under physiological and pathophysiological conditions

Area of Science:

• Endocrinology
• Chronobiology
• Computational Biology

Background:

• Thyroid-stimulating hormone (TSH) secretion exhibits a known circadian rhythm.
• Emerging evidence suggests a pulsatile release pattern of TSH.
• Understanding TSH pulsatility is crucial for interpreting endocrine function.

Purpose of the Study:

• To compare different computer-assisted methods for analyzing TSH pulsatile release.
• To investigate the relationship between TSH pulsatility and the circadian rhythm.
• To examine TSH secretion patterns in patients with thyroid disorders.

Main Methods:

• Analysis of TSH secretion in 21 healthy males using Pulsar, Cluster, and DESADE programs.
• Application of Fourier transformation to identify dominant frequencies in TSH release.
• Segmented analysis of TSH data over 8-hour intervals.
• Comparison of TSH patterns in healthy controls with patients exhibiting TSH-induced hyperthyroidism, pituitary tumors, and non-toxic goiter.

Main Results:

• Computer-assisted methods showed systematic differences in TSH pulse detection, with DESADE and Cluster identifying more pulses than Pulsar.
• Fourier analysis revealed dominant TSH secretion frequencies at 160 minutes, 24 hours, and 33 minutes.
• Approximately 50% of TSH pulses occurred between 20:00 and 04:00, highlighting the nocturnal dominance of pulsatile release.
• Patients with TSH-producing pituitary tumors lacked circadian TSH variation, while those with non-toxic goiter had lower mean TSH levels and slightly fewer pulses detected by DESADE.

Conclusions:

• The choice of computer-assisted method impacts the quantification of TSH pulsatile release.
• Nocturnal TSH pulsatility plays a significant role in generating the circadian TSH rhythm.
• TSH secretion patterns are altered in specific thyroid pathologies, particularly in pituitary tumors and non-toxic goiter.