Dissociation between TSH and prolactin dynamics in treated thyrotoxicosis

Area of Science:

• Endocrinology
• Thyroidology

Background:

• Thyroid-stimulating hormone (TSH) and prolactin secretion are typically concordant in thyroid disease.
• Previous treatments for thyrotoxicosis may alter these secretory patterns.

Purpose of the Study:

• To investigate the TSH and prolactin responses to thyrotropin-releasing hormone (TRH) infusion in euthyroid individuals previously treated for thyrotoxicosis.

Main Methods:

• TRH infusion (500 μg) was administered to euthyroid patients treated with radioactive iodine (131I) or antithyroid drugs.
• Patients were categorized based on their maximal TSH increment (deltaTSH) following TRH stimulation.
• Prolactin responses (delta prolactin) were assessed and compared across different TSH response groups.

Main Results:

• In 131I-treated patients, TSH and prolactin responses to TRH were not uniformly concordant across all groups.
• A blunted or absent TSH response to TRH persisted in many patients long after achieving euthyroidism.
• This blunted TSH response was often associated with normal or exaggerated prolactin responses.

Conclusions:

• TRH-induced TSH and prolactin responses are not consistently concordant in individuals treated for thyrotoxicosis.
• Persistent alterations in TSH responsiveness, even after restoration of euthyroid status, are common.
• The study highlights the complex and often discordant endocrine adjustments following thyrotoxicosis treatment.