Page 121 - Clinical Biochemistry

 T3 is the active hormone.
• It has many effects. Among the most prominent of these are:
(A) An increase in metabolic rate (seen by a rise in the uptake of oxygen).
(B) An increase in the rate and strength of the heartbeat.
Normal value
Normal T4 levels are:
* 7.5-16.5 ug/dl at 1-4 months
* 5.5-14.5 ug/dl at 4-12 months
* 5.6-12.6 ug/dl at 1-6 years
* 4.9-11.7 ug/dl at 6-10 years
* 4-11 ug/dl at 10 years and older.
Normal T3 levels are:
* 90-170 ng/dl at birth
* 115-190 ng/dl at 6-12 years
* 110-230 ng/dl in adulthood.
 Levels of free T4 (thyroxine not attached to TBG (thyroxine binding globulin)) are higher
in teenagers than in adults.
 Normal T4 levels do not necessarily indicate normal thyroid function.
 T4 levels can register within normal ranges in a patient who:
• Is pregnant
• Has recently had contrast X rays
• Has nephrosis or cirrhosis.
Diseases of the thyroid gland
1. Hypothyroid diseases:
• Cretinism
• Myxedema
• Goiter
2. Hyperthyroid diseases (excessive secretion of thyroid hormone):
• Graves´ disease
• Osteoporosis
Cretinism
• Hypothyroidism in infancy and childhood leads to under-developed growth and
intelligence.