A. Anterior pituitary
B. Colon
C. Gonads
D. Kidney
E. Pancreas
The correct answer is A. The anterior pituitary produces the following hormones: thyroid-stimulating
hormone (TSH), adrenocorticotropic hormone (ACTH), follicle stimulating hormone (FSH), leutinizing
hormone (LH), prolactin, and growth hormone (GH). Two of these secretions (GH, ACTH) affect the
sensitivity of peripheral tissues to the action of insulin. Growth hormone has a direct effect on liver and
muscle to decrease insulin sensitivity. This may be partly through a growth hormone-induced decline
in insulin receptors or to unknown postreceptor defects. In excess, growth hormone is "diabetogenic,"
and approximately 25% of patients with acromegaly have diabetes. ACTH indirectly has antiinsulin
effects by virtue of the cortisol secretion it evokes. Like growth hormone, cortisol also decreases
insulin sensitivity in peripheral tissues. A third anterior pituitary hormone, TSH, also tends to increase
blood glucose levels. In this case, the effect is probably mediated mostly through increased glucose
absorption by the gut. Patients with hyperthyroidism can sometimes exhibit a postprandial glucosuria
because of excessive intestinal glucose absorption. In diabetic animals, the removal of the anterior
pituitary may lower blood glucose by increasing tissue sensitivity to whatever insulin remains.
Removal of the colon (choice B) should have little effect on blood glucose because dietary glucose is
absorbed in the small intestine.
Sex steroids secreted by the gonads (choice C) have little effect on blood glucose concentration.
The kidney (choice D) plays an important role in reabsorbing filtered glucose. In diabetes, the tubular
reabsorption maximum is exceeded and glucose spills over into the urine. The loss of glucose in the
urine helps to reduce the severity of the plasma hyperglycemia. Removal of the kidneys would, if
anything, make the hyperglycemia worse. Pancreatectomy (choice E) would make the hyperglycemia
worse by removing the source of any remaining insulin.
B. Colon
C. Gonads
D. Kidney
E. Pancreas
The correct answer is A. The anterior pituitary produces the following hormones: thyroid-stimulating
hormone (TSH), adrenocorticotropic hormone (ACTH), follicle stimulating hormone (FSH), leutinizing
hormone (LH), prolactin, and growth hormone (GH). Two of these secretions (GH, ACTH) affect the
sensitivity of peripheral tissues to the action of insulin. Growth hormone has a direct effect on liver and
muscle to decrease insulin sensitivity. This may be partly through a growth hormone-induced decline
in insulin receptors or to unknown postreceptor defects. In excess, growth hormone is "diabetogenic,"
and approximately 25% of patients with acromegaly have diabetes. ACTH indirectly has antiinsulin
effects by virtue of the cortisol secretion it evokes. Like growth hormone, cortisol also decreases
insulin sensitivity in peripheral tissues. A third anterior pituitary hormone, TSH, also tends to increase
blood glucose levels. In this case, the effect is probably mediated mostly through increased glucose
absorption by the gut. Patients with hyperthyroidism can sometimes exhibit a postprandial glucosuria
because of excessive intestinal glucose absorption. In diabetic animals, the removal of the anterior
pituitary may lower blood glucose by increasing tissue sensitivity to whatever insulin remains.
Removal of the colon (choice B) should have little effect on blood glucose because dietary glucose is
absorbed in the small intestine.
Sex steroids secreted by the gonads (choice C) have little effect on blood glucose concentration.
The kidney (choice D) plays an important role in reabsorbing filtered glucose. In diabetes, the tubular
reabsorption maximum is exceeded and glucose spills over into the urine. The loss of glucose in the
urine helps to reduce the severity of the plasma hyperglycemia. Removal of the kidneys would, if
anything, make the hyperglycemia worse. Pancreatectomy (choice E) would make the hyperglycemia
worse by removing the source of any remaining insulin.
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