Figure 8. How low iodine can lead to goiter Image source: DIY SOLUTIONS Cretinism During pregnancy the mother’s thyroid hormones cross the placenta and go into the fetus. The mother’s thyroid hormones play a role in the fetus’ nervous system development, especially the brain, as early as the first trimester — before the fetus is able to produce its own thyroid hormones. However, babies born with born with low thyroid hormones have mental retardation, hearing, locomotor ability, speech and behavior challenges, as well as stunted growth. Delays in restoring normal thyroid levels can lead to irreversible damage. Parathyroid Glands The parathyroid glands are four small masses located on the posterior surface of the thyroid gland. They secrete parathyroid hormone in response to low blood calcium levels, and its effect is to increase those levels. It opposes the action of calcitonin. It does this by stimulating the release of Ca from bone into the blood, it stimulates the kidneys to reabsorb Ca and prevent it from being excreted in the urine, and it stimulates another hormone, called calcitriol, to increase absorption of calcium from intestines of the digestive system. Figure 9. Parathyroid glands
©Jano Duplication or Replication prohibited Endocrine System Page 12 of 15 Figure 10. Insulin and glucagon maintain acceptable blood glucose levels Clinical Perspectives Diabetes Mellitus
©Jano Duplication or Replication prohibited Endocrine System Page 13 of 15
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