[The causes of infertility in hyperprolactinemia]

Area of Science:

• Endocrinology
• Reproductive Medicine
• Neuroendocrinology

Background:

• Hyperprolactinemia is associated with infertility and menstrual dysfunction.
• The hypothalamohypophyseal system regulates reproductive hormones.
• Dopamine plays a key role in inhibiting prolactin secretion.

Purpose of the Study:

• To investigate the function of the hypothalamohypophyseal system in women with infertility and hyperprolactinemia.
• To assess the response of pituitary hormones to releasing hormones and a dopamine antagonist.
• To elucidate the mechanism of fertility disturbance in stable hyperprolactinemia.

Main Methods:

• Studied 28 women with hyperprolactinemic amenorrhea and 5 controls.
• Administered gonadotropin-releasing hormone (GnRH), thyrotropin-releasing hormone (TRH), and metoclopramide (dopamine antagonist).
• Measured serum levels of prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone (TSH).

Main Results:

• Lactotrophs exhibited resistance to functional tests, which increased with prolactin levels.
• Gonadotroph and thyrotroph responses to tests improved with higher degrees of hyperprolactinemia.
• Stable hyperprolactinemia appears linked to impaired lactotroph receptor function, reducing dopamine's inhibitory effect.

Conclusions:

• Stable hyperprolactinemia may result from lactotroph receptor apparatus disorder.
• This dysfunction leads to lactotroph insensitivity to dopamine's prolactin-inhibiting effects.
• A proposed scheme for fertility disturbance in stable hyperprolactinemia is discussed.