Question 11 through 21 are based on the following passage
Glands manufacture and secrete necessary substances. Exocrine glands secrete their products trough ducts, but endocrine glands, or ductless glands, release their products directly into the bloodstream.
One important endocrine glands is the thyroid gland. It is in the neck and has two lobes, one one each side of the windpipe. The thyroid gland collects iodine from the blood and produces thyroxine, an important hormone, which it stores in an inactive form. When thyroxine is needed by the body, the thyroid gland secretes it directly into the bloodstream. Thyroxine is combined int the body cells with other chemicals and effects many functions of the body.
The thyroid gland may be underactive or overactive, resulting in problem. An underactive thyroid causes hypothyroidism, while an overactive one causes Hyperthyroidism. The former problem, called myxedema in adults and cretinism in children, causes the growth process to slow down. A cretin's body and mind do not grow to their full potential. Hyperthyroidism, on the other hand, results in extreme nervousness, an increase in heart action, and other problems.
Either hypothyroidism or hyperthyroidism may result in goither, or an enlarged thyroid gland. A goiter will appear when the body is not getting enough iodine. Goiter is less common today, since most people use iodized salt.
Kieven Russia also enjoyed a century of rebirth some two hundred years later under the able rule of yaroslav the Wise. Like Charlemagne, he founded schools, established libraries, and brought about many architectural achievements.
