Hormonal Influence on Human Growth and Development

Hormone Action

Endocrinology studies the glands of internal secretion, responsible for producing hormones, chemical messengers that act on tissues and organs of our body. The pituitary gland is controlled by hypothalamic releasing factors, the thyroid gland secretes thyroxine, the pancreas secretes insulin, the adrenal glands secrete adrenaline and cortisone, and the gonads secrete sex hormones.

Growth Hormone (GH or STH)

Growth hormone originates in the anterior pituitary gland and is considered essential for normal growth. It is classified as anabolic while under the influence of the diencephalic hormone STH. It is specific to the species, and its rate decreases after the age of 30.

Features:

• Stimulates growth and metabolic functions.
• Stimulates protein synthesis and facilitates the transport of amino acids.

Its performance depends on the medium of another substance released by the liver (somatomedin), which acts on the cartilage, bones, and viscera. Its action is also favored by thyroxine and insulin.

Thyroid Hormone

Thyroxine is a calorigenic hormone (it stimulates oxygen consumption and caloric expenditure). It has more to do with nerve and bone maturation than growth in length.

Its effects are:

• Organic brain maturation.
• Maturation of nasal and orbital contour.
• Ossification of the epiphyseal cartilage.
• Acts on body proportionality.

A deficiency of this hormone causes problems in growth and slows bone and dental maturation.

Insulin, Gonadal, and Adrenal Hormones

Insulin: Originates in the pancreas. It influences the metabolism of carbohydrates and the normal growth and development of children. It contributes to the penetration into the cells of glucose, amino acids, and electrolytes, promotes DNA synthesis, protein synthesis, and the action of growth hormone.

Gonadal and Adrenal Hormones: In males, they accelerate growth in height and increase muscle mass.

Sex Determination

Sex determines differences such as body size and shape, athletic precocity in certain indices (dental and bone in girls), precocious puberty (2-year advantage for girls), as well as other body parameters.

Racial Factors

Racial factors may determine differences in a continuum that ranges from genetic to environmental. In general, we can say:

• Women are generally larger than those of other races.
• Asians are generally smaller.
• The great bodily differences appear after adolescence.