Effects of synthetic LH-RH and TRH on pituitary function in anencephalic infants

Area of Science:

• Endocrinology
• Developmental Biology
• Neuroscience

Background:

• Anencephaly is a severe congenital disorder characterized by the absence of major parts of the brain, skull, and scalp.
• The development and function of the hypothalamo-pituitary axis are crucial for fetal growth and development.
• Understanding pituitary function in anencephaly provides insights into early human endocrine development.

Purpose of the Study:

• To investigate the pituitary endocrine function in anencephalic infants.
• To assess the levels of key pituitary hormones in fetal circulation.
• To evaluate the response of the pituitary to specific releasing hormones in the absence of a developed hypothalamus.

Main Methods:

• Measurement of serum concentrations of growth hormone, prolactin, TSH, FSH, and LH in umbilical venous blood from anencephalic infants.
• Administration of gonadotropin-releasing hormone (GnRH, also known as LHRH) and thyrotropin-releasing hormone (TRH).
• Assay of hormone levels before and after the administration of LHRH and TRH to assess pituitary responsiveness.

Main Results:

• No significant differences were observed in basal levels of growth hormone, prolactin, TSH, FSH, and LH between anencephalic and normal infants.
• Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) showed no significant response after LHRH administration.
• Thyroid-stimulating hormone (TSH) levels significantly increased (4- to 6-fold) following TRH administration, indicating pituitary responsiveness.

Conclusions:

• The human fetal hypothalamo-pituitary axis initiates function by mid-pregnancy.
• The pituitary gland demonstrates responsiveness to TRH in anencephalic fetuses, suggesting TSH regulation may involve pituitary autoregulation.
• The lack of FSH and LH response to LHRH may indicate a critical role of the hypothalamus in regulating gonadotropin secretion.