3. The thyroid gland is a butterfly-shaped organ located in
the base of your neck. It releases hormones that control
metabolism—the way your body uses energy. The thyroid's
hormones regulate vital body functions, including:
Breathing
Heart rate
Central and peripheral nervous systems
Body weight
Muscle strength
Menstrual cycles
Body temperature
Cholesterol levels
3
5. How the Thyroid Gland Works
The thyroid is part of the endocrine system, which is
made up of glands that produce, store, and release
hormones into the bloodstream so the hormones can
reach the body's cells. The thyroid gland uses iodine
from the foods you eat to make two main hormones:
Triiodothyronine (T3)
Thyroxine (T4)
5
7. Thyroid Regulation
7
PLASMA T4 + FT4
HYPOTHALAMUS - TRH
ANT. PITUITARY - TSH
THYROID T4 and T3
PLASMA T3 + FT3
TISSUES FT4 to FT3, rT3
TSH -R
8. 8
The Thyroxines
Tri Iodo Thyronine – T3
- 10% is from thyroid gland
- 90% derived from conversion of T4 to T3
Tetra Iodo Thyronine – T4
- Is exclusively from thyroid gland
From the thyroid gland
- 80% of hormone secreted is T4
- 20% of hormone secreted is T3
9. Half-life of thyroid hormonesHalf-
life of thyroid hormones
T4 7days
T3 6hour
TSH <1hour
9
14. Hypothyroidism
Epidemiology
Most common endocrine disease
Females > Males – 8 : 1
Presentation
Often unsuspected and grossly under diagnosed
90 % of the cases are Primary Hypothyroidism
Menstrual irregularities, miscarriages, growth retard.
Vague pains, anaemia, lethargy, gain in weight
Hair loss, Constipation, Memory loss, Dry, rough
pale skin
Low free T4 and High TSH
14
32. Thyroid Antibodies
Anti Microsomal (TM ) Antibodies
Anti Thyroglobulin (TG) Antibodies
Anti Thyroxine PerOxidase (TPO) Ab.
Anti Thyroxine antibodies
Thyroid Stimulating (TSA) Antibodies
32
High titres TPO Ab in Hashimotos & Reidle’s thyroiditis
Anti thyroxine Ab in peripheral resistance to Thyroxine
TSA (TSI) in Graves’ Hyperthyroidism
34. ECG finding in hypothyroidism
Sinus Bradycardia
Low voltage
Prolongation of the PR interval
Bundle branch blocks Flattening or inversion of the T
wave
Ventricular premature contractions (VPS)
Sustained or non-sustained attacks of ventricular
tachycardia (VT)
Prolongation of the QT interval
36. 36
Algorithm for Hypothyroidism
Measure TSH
Elevated TSH Normal TSH
Measure FT4 Considering Pituitary
Normal Low No Yes
Sub-clinical hypo
TPO + TPO -
T4 repl Annual FU
Primary hypothyroid
TPO + TPO -
No tests Measure FT4
Low Normal
No tests
Evaluate Pituitary
Sick Euthyroid
Drugs effect
Hashimoto
Others
37. TREATMENT
The goal of hypothyroidism therapy is to replace
thyroxine to mimic normal, physiologic levels and
alleviate signs, symptoms, and biochemical
abnormalities
37
38. Treatment of choice:
levothyroxine (synthetic levothyroxine, LT4)
Dose of Levothyroxine depends on the degree of Hypothyroidism, Age &
General health condition of the patient
Usually daily replacement dose is 1.6µgm/Kg body weight
Start with Low Dose
Patients under age 60, without cardiac disease can be started on 50 – 100
μg/day. Dose adjusted according to TSH levels
Chemically stable
In elderly patients or those with heart disease, start low and go slow (12.5–25.0
μg/day; then slowly ↑ the dose by 25-μg increments every month until
euthyroid).
Other therapies (T3 or T3 and T4 mixtures)
no advantages versus levothyroxine
38
39. Factors That May Reduce
Levothyroxine Effectiveness
Malabsorption Syndromes
Postjejunoileal bypass
surgery
Short bowel syndrome
Drugs That Increase Clearance
Rifampin
Carbamazepine
Phenytoin
Factors That Reduced T4 to T3 conversion
Amiodarone
Selenium deficiency
39
40. Follow up
Serum TSH levels should be measured after 6-8 weeks
of therapy and dosages should be adjusted accordingly
Target TSH levels should be between 1-2 mU/l
Once a stable TSH is achieved, it should be estimated
every year
41. 41
How the patient improves
Feels better in 2 – 3 weeks
Reduction in weight is the first improvement
Facial puffiness then starts coming down
Skin changes, hair changes take long time to regress
TSH starts showing decrements from the high values
TSH returns to normal eventually
42. COMPLICATIONS
Myxedema coma: Characterized by weakness,
hypothermia, hypoventilation with hypercapnia,
hypoglycemia, hyponatremia, water intoxication, shock,
and death. Treatment is supportive therapy with
rewarming, intubation, and IV LT4. Often precipitated by
infection or other forms of stress. Consider glucocorticoids
for AI, which can coexist with thyroid disease.
Other complications: Anemia (normocytic), CHF,
depression, and lipid abnormalities (elevated LDL and TG)
42