Hypersecretion of FSH in infant boys and girls born small for gestational age

Area of Science:

• Reproductive Endocrinology
• Pediatric Endocrinology
• Developmental Biology

Background:

• Prenatal growth restriction (low birthweight) is linked to later reproductive issues, including elevated FSH and smaller gonadal size.
• The early impact of low birthweight on the follicle-stimulating hormone (FSH) and inhibin B feedback loop during infancy remains unclear.
• Infancy presents a critical window to investigate early effects on the gonadal axis due to its high activity.

Purpose of the Study:

• To investigate the early effects of prenatal growth restriction on the FSH-inhibin B feedback loop in infancy.
• To assess serum concentrations of reproductive hormones in infants appropriate for gestational age (AGA) versus small for gestational age (SGA).

Main Methods:

• Serum FSH and inhibin B levels were measured in 46 infants (3-6 months old).
• Hormone levels (FSH, LH, E2, inhibin B, free androgen index) were compared between AGA and SGA infants.
• Infants were categorized by gestational age and birthweight (AGA vs. SGA).

Main Results:

• Small for gestational age (SGA) infants showed significantly higher serum FSH levels compared to appropriate for gestational age (AGA) infants (2-fold higher in girls, 4-fold higher in boys).
• Serum levels of luteinizing hormone (LH), inhibin B, and androgens/estrogen were comparable between SGA and AGA infants.
• These findings indicate elevated FSH in both SGA boys and girls during infancy.

Conclusions:

• Prenatal growth restriction is associated with elevated serum FSH concentrations in infancy for both genders.
• SGA infants may require increased FSH stimulation to maintain normal inhibin B production, highlighting an adaptation in the feedback loop.
• These findings extend the known endocrine consequences of early growth restriction to the reproductive axis in both sexes, with potential implications for future fertility.