ABNORMALITIES OF THYROID FUNCTION
Dr. Shaikh Mujeeb AhmedAssistant ProfessorAlMaarefa College
ENDO BLOCK 412
Objectives
• The student should be able to:• Describe the etiology, symptoms and
treatment of thyrotoxicosis and hypothyroidism.
Abnormalities
• Hypothyroidism– Deficient thyroid hormone secretion
• Hyperthyroidism• Excess thyroid hormone secretion
Hypothyroidism
• Primary failure of thyroid gland itself• Secondary to deficiency of TRH, TSH or both.• From an inadequate dietary supply of iodine.
Clinical features• The symptoms of hypothyroidism are largely caused by a
reduction in overall metabolic activity. • Reduced BMR (less energy expenditure at rest); • Displays poor tolerance of cold (lack of the calorigenic effect); • Tendency to gain excessive weight (not burning fuels at a normal
rate); • Easily fatigued (lower energy production); • Slow, weak pulse (caused by a reduction in the rate and strength
of cardiac contraction and a lowered cardiac output); and• Exhibits slow reflexes and slow mental responsiveness (because
of the effect on the nervous system). The• Mental effects are characterized by diminished alertness, slow
speech, and poor memory.
Causes of congenital hypothyroidism
• Maternal iodine deficiency• Fetal thyroid dysgenesis• Inborn errors of thyroid hormone synthesis• Maternal antithyroid antibodies that cross the
placenta • Fetal hypopituitary hypothyroidism
MYXEDEMA (Adult Hypothyroidism)
Puffy appearance, primarily of face, hands, and feet
Caused by infiltration of skin with complex water retaining carbohydrate molecules.
Symptoms: The patient becomes sluggish both mentally and physically and often feels cold. The hair becomes dry and the skin becomes dry and waxy. The tissues of the face swell.
Treatment: – If diagnosed early, can be treated by
administrating of T4. – Exception, if hypothyroidism caused by
iodine deficiency; treated by dietary iodine.
Cretinism• Results from hypothyroidism from birth • Characterized by dwarfism & mental retardation as
well as other general symptoms of thyroid deficiency. • At birth, child appears normal because thyroxine is
received from mother through placenta • Symptoms: growth retardation, abnormal bone
development, low body temperature, lethargy, severely mentally retarded (short limbs, a large protruding tongue, coarse dry skin, poor abdominal muscle, tone and an umbilical hernia).
Cretinism
HYPERTHYROIDISM
• The most common cause of hyperthyroidism is Graves’ disease.• immune disease• thyroid-stimulating immunoglobulin (TSI), also known as long-acting thyroid
stimulator (LATS),• ↑ BMR • poor tolerance of heat• Increased appetite • body weight• muscle weakness • Muscle termers• Sleep• ↑ Heart rate• ↑COP• Irritable, tense, anxious• Exophthalmos (bulging eyes) (grave’s disease)
Fig. 19-4, p. 696
Fig. 19-5, p. 697
• Anti thyroid drugs• Surgical removal• Administration of radioactive iodine
GOITER
• A goiter is an enlarged thyroid gland.
• Occurs when either TSH or TSI excessively stimulates the thyroid gland.
• The most common cause of goiter worldwide is a lack of iodine in the diet.
Causes of Goiter
• Iodine deficiency• Graves' disease• Hashimoto's disease• Multinodular goiter• Solitary thyroid
nodules• Thyroid cancer• Pregnancy• Inflammation
Fig. 19-6, p. 697
Table 19-1, p. 696
Synthesis, storage, and secretion of thyroid hormone
Thiocynate
XX
Thiouracil
Antithyroid Substances
• Thiocyanate Ions – Decrease Iodide Trapping– inhibition of the iodide-trapping mechanism
• Propylthiouracil – Decreases Thyroid Hormone Formation
Propylthiouracil & similar compounds as– methimazole and carbimazole– block the peroxidase enzyme
• Iodides in high concentrations decrease thyroid activity and thyroid gland size
19
References
Human physiology, Lauralee Sherwood, seventh edition.
Text book physiology by Guyton &Hall,11th edition.
Text book of physiology by Linda .S .Costanzo third edition