thyroid & hypothyroid

1. THYROID
DISORDERS
D R S R A V A N K U M A R G
M . D . M E D I C I N E ( P G I M E R )
A S S I S T A N T P R O F E S S O R
M R I M S

2. 20 gm

5. SYNTHESIS OF THYROXIN
1) Synthesis of Thyroglobulin
2) Iodide Trapping (NIS) - PENDRIN
3) Iodination of Tyrosine located on Thyroglobulin
molecule(TPO)
4) Release of Thyroglobulin into follicular lumen
5) Reabsorption of Thyroglobulin+ T4/T3/MIT/DIT from lumen
into follicular cell
6) Hydrolysis of Thyroglobulin to release Thyroxine (T4)and Tri
Iodo thyronine (T3)
7) After release in to circulation a part of it binds to
globulin(TBG) and albumin ( ie binds to proteins)

7. • Free hormone is available to the tissues for intracellular
transport and feedback regulation that induces its metabolic
effects and that undergoes deiodination or degradation.
• The bound hormone acts merely as a reservoir

9. SELENODEIODINASES

10. PHYSIOLOGICAL ACTIONS OF THYROXINE
1) Calorigenic: Energy production & metabolism of tissues
2) Carbohydrate metabolism: Glucose production
3)Protein Metabolism: Moderate conc: Anabolic effect
High conc.: Catabolic effect
4)Lipid Metabolism: Cholesterol levels – Inversely proportional
5) Calcium : removes calcium from bones - osteoporosis
6) Growth: Important for growth
7) Mammary glands: output of milk
8) Heart Rate: heart rate
9) Brain: Important for normal emotional responsiveness, cerebral
activity, sensory activity

12. LABORATORY ASSESSMENT OF THYROID STATUS
• TSH – 0.4 to 4 mU/L
• TSH – 0.1 to 0.4 – Sublinical hyperthyroidism
• TSH – 4 to 10 – Subclinical hypothyroidism
• T4 - 5 to 11 µg/dL
• T3 - 70 to 190 ng/dL
• Free T3 & Free T4
• Serum thyroglobulin (thyrotoxicosis factitia)
• Anti Tg – Ab
• Anti – TPO Ab
• TSHR- Ab

13. RADIOIODINE UPTAKE
• I 131 (half-life 8.1 days) and I 123 (half-life 0.55 day) both
emit gamma radiation, which permits their external detection and
quantitation at sites of accumulation, such as the thyroid

14. HYPOTHYROIDISM

16. SKIN AND APPENDAGES
• Increased glycosaminoglycan – hyaluronic acid in dermis traps
water
• causing skin thickening without pitting (Myxedema)
• Myxedematous tissue is boggy and nonpitting
– around the eyes
– on the dorsa of the hands and feet
– supraclavicular fossae
– enlargement of the tongue
– thickening of the pharyngeal and laryngeal mucous membranes.
• skin is pale and cool - cutaneous vasoconstriction
• Skin id dry & coarse – reduced secretions of the sweat glands and
sebaceous glands - ichthyosis.
• Hair is dry and brittle, lacks luster, and tends to fall out
• hypercarotenemia - skin has yellow tint – no scleral icterus
• Poor wound healing & easy bruising

17. CARDIOVASCULAR SYSTEM
• Reduction in both stroke volume and heart rate .
• Peripheral vascular resistance at rest is increased, narrowing of
pulse pressure, decrease in blood flow to the tissues.
• effusion into the pericardial sac of fluid rich in protein and
glycosaminoglycans
• elevations of total and low-density lipoprotein (LDL) cholesterol
• risk factor for atherosclerosis and cardiovascular disease

18. RESPIRATORY SYSTEM
• Pleural effusions
• Alveolar hypoventilation and carbon dioxide retention
(myxedema coma)
• obstructive sleep apnea

19. GASTROINTESTINAL
SYSTEM
• Weight gain
• Reduced apetite
• Constipation
• pernicious anemia (antibodies against gastric parietal cells )
• NAFLD

20. CENTRAL AND PERIPHERAL NERVOUS SYSTEMS
• Defciency in fetal life or at birth impairs neurologic development,
hypoplasia of cortical neurons with poor development of cellular
processes, retarded myelination, and reduced vascularity
• Thick, slurred speech and hoarseness - myxedematous
infltration of the tongue and larynx
• intellectual functions - reduced, Loss of initiative, and memory
defects
• Lethargy, somnolence, depression, dementia
• Coma
• Numbness and tingling of the extremities – CTS
• hung-up reflexes -decrease in the rate of muscle contraction and
relaxation

21. Muscular System
•Stiffness and aching of muscles
•Delayed muscle contraction and relaxation cause slowness of movement and
delayed tendon jerks
•Serum levels of homocysteine, creatine kinase, aspartate aminotransferase,
and
lactate dehydrogenase may be increased in hypothyroidism
Hematopoietic System
• Mild normocytic, normochromic anemia
•Macrocytic – b12 deficient
Pituitary
•Increased serum prolactin levels, stimulated by the elevation in TRH - TSH
elevation - galactorrhea
Reproductive Function
•diminished libido and failure of ovulation
• excessive and irregular breakthrough menstrual bleeding

22. INVESTIGATIONS
• TSH (> 10) , T3, T4 – low
• Anti TPO Ab

24. TREATMENT
• Levothyroxine 1.6 µg/kg ideal body weight per day taken on empty
stomach
• 7-day half-life, approximately 6 weeks are required before there is
complete equilibration of the fT4 and the biologic effects of
levothyroxine
• long half-life - it is safe for a patient to take any missed doses of T4
for up to a week after missing tablets.
• Check TSH after 6 weeks
• Target normal TSH & High normal T4
• CAD:
Start 25 µg/day – increase 12.5 µg every 2 months
• Myxedema Coma
• Levothyroxine 500 µg through NG tube
• Inj Hydrocortisone 50 mg i.v 6 hourly

25. THYROIDITIS

27. THYROTOXIC/
DESTRUCTIVE
HYPOTHYROID
RECOVERY

28. HASHIMOTO’S THYROIDITIS
• High serum thyroid antibody concentrations and goiter,
• Hashimoto’s thyroiditis is the most frequent cause of
hypothyroidism and goiter
• Anti TPO Ab

29. SUPPURATIVE THYROIDITIS/ACUTE
THYROIDITIS
• Bacterial infection, but fungal, mycobacterial, or parasitic
infections may also occur as the cause
• Immunosupressed individuals

30. PAINFUL SUBACUTE
THYROIDITIS
• frequently follows an upper respiratory tract infection
• Viral

31. PAINLESS POSTPARTUM THYROIDITIS /
PAINLESS SPORADIC THYROIDITIS
• Autoimmune
• Anti TPO Ab

32. HYPOTHYROIDISM
IN PREGNANCY

33. NORMAL TSH IN PREGNANCY
• 1 st trimester – 0.1 to 2.5 mU/L
• 2 nd trimester – 0.2 to 3 mU/L
• 3 rd trimester – 0.3 to 3 mU/L
• Increase dose of Levothyroxine
by 30% after confirmation of
pregnancy
TREATMENT: 2 µg/kg
Monitor TSH, Free T4 monthly x
Initial half of pregnancy

34. THANK YOU