Thyroid
Hypothyroidism
Symptoms
- Weakness
- Fatigue
- Memory impairment
- Cold intolerance
- Constipation
- Loss of hair
- Hoarseness
- Deafness
- Menstrual irregularity
Signs
- Dry coarse skin
- Periorbital edema
- Coarse thin skin
- Thick tongue
- Slow speech
- Deep voice
- Delayed Achilles' tendon reflex time
- Bradycardia
Primary hypothyroidism
- Hashimotto's thyroiditis / Family history or the presence in the patient of other autoimmune
endocrine disease
- Schmidt's syndrome / Hashimotto's and Pernicious anemia and Diabetes
Mellitus
- Idiopathic
- Post therapy for hyperthyroidism
- Radioactive iodine therapy / History of radioactive iodine therapy
- Subtotal thyroidectomy / History of thyroidectomy
-
External beam radiotherapy / history of neck radiation for lymphoma or head
and neck cancer
- Lithium, Amiodarone
- Iodide deficiency / underdeveloped countries
Secondary hypothyroidism
- Hypothalamic dysfunction / symptoms of hypothalamic disease such as diabetes
insipidus, narcolepsy, excessive appetite or marked anorexia, hyperthermia
or marked hypothermia.
- Therapeutic irradiation
- Hypothalamic tumor (germinoma, meningioma,
hamartoma)
- Pituitary dysfunction /secondary adrenal insufficiency
, hypogonadism, growth hormone deficiency
- Pituitary tumor / a space-occupying mass such as headache, bitemporal
hemianopsia, 3rd, 4th, or 6th nerve defects, seizures, rhinorrhea,
meningitis
- Post partum Pituitary necrosis / history of shock or massive hemorrhage at time of
delivery as well as inability to breast feed and amenorrhea afterwards
- Sarcoidosis / symptoms of systemic illness
- Metastatic carcinoma involving pituitary, hypothalamus or
stalk
- Rathke's cleft cyst, craniopharyngioma, carotid artery
aneurysm compressing pituitary
Tests that would help confirm the diagnosis of hypothyroidism
- Total T4: Low
- Free T4: Low
- Free T3: of no value
- TSH
- Increased / Primary
- Decreased / secondary
- TRH stimulation: Primary / Exaggerated TSH response
- Thyroid autoantibodies are insensitive
- Diagnostic tests for secondary Hypothyroidism / Pituitary / Hypothalamic
dysfunction
Tests helpful in the diagnosis of secondary hypothyroidism
- MRI with gadolinium enhancement to document the presence of
a mass
- Baseline and dynamic anterior pituitary hormone testing for
deficiencies and overproduction
- Testing for other tumor markers (alpha subunits)
Non specific lab abnormalities of hypothyroidism
- CPK
- Anemia
- Bradycardia, low voltage and non specific ST T wave changes
- Hypoxia with hypercapnea
Treatment options for primary hypothyroidism
-
Thyroid hormone replacement therapy with non-generic l-thyroxin or a generic
form that has undergone rigorous quality controlled supervision of the
manufacturing process.
- With risk factors for coronary arterial disease, it would be wise to start
with a low dose of thyroid hormone and raise the dose slowly.
Treatment options for secondary hypothyroidism
- Evaluate if secondary hypoadrenalism is present.
- If present treat simultaneously with the treatment of the
hypothyroidism.
- Also evaluate whether hypogonadism and/or growth hormone
deficiency is present and treat accordingly.
- Then treat the cause of the secondary hypothyroidism.
Components of Total serum throxine
- Free thyroxine 0.03%
- Thyroxine binding albumin 10%
- Thyroxine binding prealbumin 20%
- Thyroxine binding globulin 70%
Alterations in these binding proteins can alter serum thyroxine values and
mistaken diagnosis of hypo or hyperthroism can be made.
Euthyroid hypothyroxinemia / sick syndrome
- Clinical picture
- Normal sized thyroid gland
- Low serum TBG
- Hypoalbuminemia / Nephrotic syndrome, Cirrhosis
- Low serum total T4
- Normal free T4
- Normal TSH
- TSH response to TRH normal
Subclinical hypothyroidism
- Euthyroid
- Normal serum T4 and T3
- Elevated TSH
Hyperthyroidism
Symptoms: Potentiation of sympathetic system by excess
Thyroxine
Signs:
-
Thyroid enlargement
-
Potentiation of sympathetic system by excess Thyroxine
-
Lid lag
-
Warm moist skin
-
Fine tremor
-
Brisk reflexes
-
Tachycardia
-
Onycholysis / Plummer's nails
-
Mucopoysaccharide infiltration
Etiology
Tests
- Total T4: high
- Free T4: High
- Free T3: High
- TSH: Decreased
- TRH stimulation : Flat TSH response
- RAIU/ Scintiscan
- Increased / Graves
- Heterogynous / Thyroiditis, Multinodular goiter
- Hot nodule / Toxic adenoma
- Decreased / Factitious and struma ovari and Thyroiditis
- TRAb
- TSI
- Sonography: Serial size of thyroid nodule on T4 suppressive therapy
Euthyroid hyperthyroxinemia (alterations in TBG)
- High serum TBG
- Estrogens, Hepatitis, 5-fluorouracil
- High serum total T4
- Normal free T4
- Normal TSH
Euthyroid hyperthyroxinemia (unrelated to TBG)
- Clinical picture
- Normal sized thyroid gland
- High serum total T4
- High free T4
- Acute non-thyroidal illness, Psychiatric illness, drugs
Treatment options
- Antithyroid drug therapy
- Radioactive iodine therapy
- Surgery
- Symptomatic therapy with beta blockers
Treatment options based on etiology
- Graves disease
- Toxic multinodular goiter
- Toxic adenoma
- Thyroiditis / Symptomatic therapy only
- Factitious Thyrotoxicosis / Treat the personality problem