The development of the small intestine

Area of Science:

• Gastroenterology
• Developmental Biology
• Endocrinology

Background:

• Gastrointestinal (GI) function development shows remarkable coordination, suggesting central regulatory mechanisms.
• Hormones, such as thyroxine and corticosteroids, are implicated in the precocious development of GI enzyme and transport functions.
• Hormonal roles in GI development may be primary or permissive, influenced by biological clocks or signals like body size and nutrient intake.

Purpose of the Study:

• To explore the central mechanisms coordinating the development of various gastrointestinal functions.
• To investigate the role of hormones and other biological signals in postnatal GI development.

Main Methods:

• The study reviews existing research on hormonal and environmental influences on GI development.
• It discusses the effects of hormone administration (thyroxine, corticosteroids) and removal (thyroidectomy, adrenalectomy) on GI maturation.
• The role of biological clocks (chronologic age) and biological signals (body size, oral intake) is considered.

Main Results:

• Exogenous thyroxine and corticosteroids can induce precocious development of GI enzyme and transport functions.
• Thyroidectomy and adrenalectomy disrupt the normal pattern of postnatal GI development.
• Postnatal increases in intestinal mucosal surface area, brush border enzymes, and carrier-mediated transport are observed.

Conclusions:

• Central mechanisms, potentially hormonal, coordinate GI development.
• Genetic factors establish the pattern, but environmental factors like nutrient intake modify these adaptive changes.
• Hormonal activation may be controlled by genetic programming (biologic clock) or external cues (body size, nutrient intake).