Increased thyrotrophin secretion induced by sulpiride in man

Area of Science:

• Endocrinology
• Neuroendocrinology

Background:

• Thyroid-stimulating hormone (TSH) regulates thyroid hormone production.
• The role of dopaminergic mechanisms in TSH regulation is not fully understood.

Purpose of the Study:

• To investigate the effect of sulpiride, a dopamine-receptor antagonist, on TSH levels in humans.
• To explore the potential dopaminergic control of TSH release.

Main Methods:

• Administration of 100 mg intramuscular sulpiride to normal women, women with galactorrhea, and patients with primary hypothyroidism.
• Administration of 150 mg oral sulpiride daily for 15 days to normal women.
• Measurement of plasma TSH and prolactin (PRL) levels.

Main Results:

• Intramuscular sulpiride significantly increased TSH in normal women, women with galactorrhea, and especially in hypothyroid patients.
• A positive correlation was observed between basal TSH and its increment after sulpiride in hypothyroid patients.
• Sulpiride also stimulated PRL release in subjects with normal PRL levels.
• No significant TSH changes were observed in normal males.
• Continuous oral sulpiride administration enhanced TSH in normal women.

Conclusions:

• TSH release is modulated by a dopaminergic mechanism in humans.
• The heightened TSH response in hypothyroid patients may be due to reduced negative feedback from thyroid hormones.