1. THYROID DYSFUNCTION Dr. Hany Ahmed
Assistant Professor of Physiology (MD, PhD).
Al Maarefa Colleges (KSA) & Zagazig University (ARE)
Specialist of Diabetes, Metabolism and Obesity
Zagazig Obesity Management & Research Unit

2. Objectives The student should be able to:
Describe the etiology, symptoms and treatment of thyrotoxicosis.
Describe the etiology, symptoms and treatment of hypothyroidism.

4. DISORDERS OF THYROID FUNCTION
Hypothyroidism:
- Deficient thyroid hormone secretion.
Hyperthyroidism:
- Excess thyroid hormone secretion.

5. Hypothyroidism Deficient thyroid hormones secretion:
In infants & children: Cretinism
In adults: Myxedema

6. Hypothyroidism Causes: Primary failure of thyroid gland itself.
Secondary to deficiency of TRH or TSH or both.
Inadequate dietary supply of iodine.

7. 1- Cretinism Hypothyroidism in utero or early life
Causes:
1- Complete absence of thyroid gland.
2- Metabolic defect (the gland is unable to make hormones).
Clinical picture: The defect is usually detected at 6 months of age.
- The infant is Idiot (mentally retarded) with coarse facies.
- Short child with short limbs.
- Dry skin, scanty hair & Large protruding tongue & open mouth.
- Depressed nose due to delayed bone growth.
- Delayed teeth eruption, defective speech & hoarsy cry.
- Weak abdominal wall, bulging abdomen and umbilical hernia.

8. - Delayed walking, sitting , Incontinent to urine & stool.
- Hypothermia (↓ BMR) & ↑ Serum cholesterol.
- Hypogonadism
Treatment: Thyroxin for life (as early as possible).

9. Cretinism & Dwarfism

10. 2- MYXEDEMA Hypothyroidism in adults due to:
1- Damage of thyroid tissue (autoimmune disorder).
2- After unavoidable surgical removal.
3- Metabolic defect.
C/P:
A reduction in overall metabolic activity & Reduced BMR.
Displays poor tolerance of cold.
Dry cold skin.
Puffy appearance of face.
Tendency to gain excessive weight.
Easily fatigued (lower energy production).
Appetite loss & constipation.

11. MYXEDEMA
8) Slow and weak pulse (caused by a reduction in the rate and strength of cardiac contraction and a lowered cardiac output).
9) Slow reflexes, slow mental responsiveness, diminished alertness, slow speech, sleepiness and poor memory.
10) Hair loss in head and outer of eye brow (vitamin A deficiency).
11) Arteriolosclerosis ( Serum cholesterol).
12) Accumulation of muco-proteins & fluids in subcutaneous tissues  non pitting edema.
13) Anemia.
Treatment:
– If diagnosed early, can be treated by administrating of T4
– Hypothyroidism caused by iodine deficiency; treated by dietary iodine.

12. HYPERTHYROIDISM
The most common cause of hyperthyroidism is Graves’ disease.
Autoimmune disease  Excessive production of thyroid hormones due to presence of some antibodies (LATS = Long Acting Thyroid Stimulator or thyroid-stimulating immunoglobulin (TSI).
C/P:
Eye:
Exophthalmos: protrusion of eye ball. Due to deposition of fat and edema behind eye ball. It is associated with lid retraction, pupillary dilatation, congestion and oedema

15. Thyrotoxicosis Effects of excess thyroxin:
 BMR & O2 consumption  sensitivity to heat.
Loss of weight in spite of  appetite &  GIT motility  diarrhea.
↑ Protein catabolism  muscle weakness.
Mobilization of fat & ↓ blood cholesterol level.
↑ Blood glucose with mild glycosuria.
Demineralization of bones ↑ Ca++ and P04 excretion in urine.
↑ Nervous excitability (fine tremors of outstretched hands & insomnia).
↑ Heart rate, COP, ABP & water hammer pulse  heart failure.

16. Thyrotoxicosis
Sympathetic potentiation: Due to  number & affinity of receptors to catecholamine. Tachycardia, sweating, tremors, anxiety.

18. Role of thyroid-stimulating immunoglobulin in Graves’ disease:
Thyroid-stimulating immunoglobulin (TSI), an antibody erroneously produced in the autoimmune condition of Graves’ disease, binds with TSH receptors on thyroid gland and continuously stimulates thyroid hormone secretion outside the normal -ve feedback control system.

19. Treatment of thyrotoxicosis
Anti-thyroid Drugs: Carbimazol is drug of choice.
Subtotal surgical removal: The gland must be controlled before operation; iodine is given for 7 days to diminish vascularity and size (Wolff-Chaikoff effect).
Destruction by irradiation: Iodine I131 is used.

20. GOITER Goiter is an enlargement of thyroid gland.
Simple goiter: due to deficiency of iodine supply   thyroid hormones formation   TSH   thyroid growth.
Exophthalmic goiter: Occurs when TSI excessively stimulates the thyroid gland.
Goiter with hypofunction.

23. 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