Khi suy nghĩ về gã khổng lồ và sao lùn, điều quan trọng cần lưu ý những hạn chế của hành động GH. Văn học trẻ em làm cho việc sử dụng thường xuyên của các tiềm năng di truyền hạn trong các cuộc thảo luận chẩn đoán và điều trị các rối loạn tăng trưởng. Dự đoán cao như thế nào một đứa trẻ | Growth Hormone 331 When thinking about giants and dwarfs it is important to keep in mind the limitations of GH action. The pediatric literature makes frequent use of the term genetic potential in discussions of diagnosis and treatment of disorders of growth. Predictions of how tall a child will be as an adult are usually based on the average of parental height plus inches for boys or minus inches for girls. We can think of GH as the facilitator of expression of genetic potential for growth rather than as the primary determinant. The entire range over which GH can influence adult stature is only about 30 of genetic potential. A person destined by genetic makeup to attain a final height of 6 feet will attain a height of about 4 feet even in the absence of GH and is unlikely to exceed 8 feet in height even with massive overproduction of GH from do not understand what determines genetic potential for growth but it is clear that although both arise from a single cell a hypopituitary elephant is enormously larger than a giant mouse. Within the same species something other than aberrations in GH secretion accounts for the large differences in size of miniature and standard poodles or chihuahuas and great danes. Synthesis Secretion and Metabolism Although the anterior pituitary gland produces at least six hormones more than one-third of its cells synthesize and secrete GH. In humans the 5 to 10 mg of stored GH make it the most abundant hormone in the pituitary accounting for almost 10 of the dry weight of the gland. More than 10 times as much GH is produced and stored as any other pituitary hormone. Of the GH produced by somatotropes 90 is composed of 191 amino acids and has a molecular weight of about 22 000. The remaining 10 called 20K GH has a molecular weight of 20 000 and lacks the 15-amino-acid sequence corresponding to residues 32 to 46. Both forms are products of the same gene and result from alternate splicing of the RNA transcript. Both forms of
