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Prolactin suppresses GnRH but not TSH secretion
G Page-Wilson1, P C Smith, C K Welt
1Reproductive Endocrine Unit, Department of Medicine, Massachusetts General Hospital, and Harvard Medical School, Boston, MA 02114, USA.
Hormone Research
|December 17, 2005
Summary
Hyperprolactinemia suppresses luteinizing hormone (LH) secretion in women, indicating gonadotropin-releasing hormone (GnRH) sensitivity. However, thyroid-stimulating hormone (TSH) secretion remains unaffected, suggesting a specific impact on reproductive hormones.
Area of Science:
- Reproductive Endocrinology
- Neuroendocrinology
Background:
- Prolactin influences dopamine, which affects GnRH and TSH secretion in animal models.
- Investigating prolactin's effect in women provides insight into human short-feedback dopamine loops.
Purpose of the Study:
- To determine if hyperprolactinemia suppresses GnRH and TSH secretion in women.
- To examine the impact of elevated prolactin on reproductive hormone regulation.
Main Methods:
- Six female subjects received recombinant human prolactin (r-hPRL) injections and infusion.
- Blood samples were collected frequently to measure LH and TSH pulse patterns during control and hyperprolactinemic states.
Main Results:
- Hyperprolactinemia significantly decreased LH pulse frequency (p<0.05) but did not alter LH pulse amplitude or mean levels.
- No significant changes were observed in TSH pulse frequency, mean, or peak levels.
- Estradiol, inhibin A/B, and menstrual cycle length remained unaffected by the induced hyperprolactinemia.
Conclusions:
- Hyperprolactinemia suppresses pulsatile LH secretion, suggesting GnRH sensitivity in humans.
- TSH secretion is not suppressed by hyperprolactinemia, indicating differential regulation.
- Short-term hyperprolactinemia does not disrupt menstrual cyclicity despite altered LH pulsatility.