HYPOTHYROIDISM

 Hypothyroidism(underactive thyroid) is a condition in which thyroid gland doesn't produce enough thyroid hormone

PRIMARY HYPOTHYROIDISM

1. Thyroid gland is involved
2. T4 DECREASED , T3 DECREASED , TSH  INCREASED(T4↓,T3↓,TSH↑)
3. CAUSES : INDIA most common cause HASHIMOTO THYROIDITIS , GLOBALLY - ENDEMIC GOITER
4. ENDEMIC CRETINISM - Body with hypothyroidism since birth
5. Food goitrogen - cabbage , 
6. Drug induced hypothyroidism : Amiodarone

SECONDARY HYPOTHYROIDISM

1. Pituitary gland is involved
2. T4 DECREASED , T3 DECREASED , TSH DECREASED(T4↓,T3↓,TSH↓)
3. CAUSES : SHEEHAN SYNDROME (Pituitary infarction)
4. Non  obstetric cause of pituitary damage called as simmond's disease - occurs due to AVM rupture ,HTN , Trauma , sickle cell anemia
5. Cranial radiation/sarcoidosis
6. Empty sella syndrome / CSF leak syndrome 

CLINICAL FEATURES :

1. Cold intolerance
2. Myxedema (alopecia , puffy face , Hoarseness voice , thick coarse skin , constipation)
3. Menorrhagia and infertility
4. Headache
5. Galactorrhea (TRH stimulate anterior pituitary to produce TSH and PROLACTIN)

ON EXAMINATION

1. Bradycardia
2. Pale yellow skin (occur due to β carotenemia)
3. Hypertension
4. Coarse /dry skin
5. Hung up ankle jerk - most reliable sign (occur due to myxedema)

WORKUP :

Thyroid function test - Total T4 , T3 Decreased ; Free T4 , T3 Decreased

Primary Hypothyroidism

TSH is high

Defect is in thyroid gland

Next investigation - Anti - TPO (thyroid peroxidase ) Ab

Secondary Hypothyroidism

TSH is low 

Pituitary defect

investigation - MRI head

TREATMENT :

LEVOTHYROXINE

If dose is ＞ 100mg, it increase oxygen consumption resulting in angina (so, a very careful titration of  dose increments should be done)

 

COMPLICATIONS :

1. Myxedema coma
2. Myxedema madness (psychosis)
3. Myxedema heart / serous cavity effusion
4. Macrocytic anemia
5. Accelerated atherosclerosis