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Clinical Application
Hypothyroidism and
Hyperthyroidism
Gail Nunlee-Bland, M.D.
Hypothyroidism

Clinical condition associated with
decreased function of the thyroid
gland and a decrease in the
circulating level of thyroid hormones
Hypothyroidism
Causes

Three categories
– permanent loss or atrophy of thyroid tissue
(primary hypothyroidism)
– compensatory thyroid enlargement due to
transient or progressive impairment of
hormone biosynthesis (goitrous
hypothyroidism)
– insufficient stimulation of a normal gland as a
result of hypothalamic or pituitary disease
(secondary hypothyroidism)
Primary Atrophic
Hypothyroidism
Autoimmune thyroiditis (Hashimoto’s
disease)
 Postablative I 131 or surgery
 Athyreotic due to ageneisis or
dysplasia
 Unresponsivenes to TSH

Goitrous Hypothryoidism
Hashimoto’s thyroiditis
 Endemic iodine deficiency
 Iodine-induced
 Antithyroid agents

Central Hypothyroidism
Secondary (pituitary) hypothyroidism
 Panhypopituitarism
 Isolated TSH deficiency
 Abnormal TSH synthesis or receptor
defect
 Hypothalamic hypothyroidism

Autoimmune Thyroiditis
More common in women
 Thyroid autoantibodies present

– autoantibodies to thyroid peroxidase
(TPOAB)
– autoantibodies to thyroglobulin (TgAb)

May be associated with other
autoimmune diseases
Postablative Hypothyroidism
Common cause of thyroid failure in
the adult
 Follows total thyroidectomy
secondary to thyroid cancer or
subtotal thyroidectomy for Graves’
disease
 Following treatment with radioactive
iodine

Athyreotic Hypothyroidism
Development defects of the thyroid
 Incidence 1 in every 4000 newborns
 Defects

– complete absence
– failure of thyroid to descend properly
during embryologic development
Hashimoto’s Thyroiditis
Most common cause of goitrous
hypothyroidism in iodine sufficient
areas
 Autoimmune

Endemic Goiter
Environmental iodine deficiency
 Affects more than 200 million people
throughout the world
 Most common in mountainous areas
- Alps, Himalayas, and Andes
 Consumption of cassava meal may
aggravate

Antithyroid Agents
Lithium
 Para-aminosalicylic acid
 Phenylbutazone
 Topically applied resorcinol
 ethionamide
 Soybean in infant formulas

Iodine-induced

Chronic administration of large
doses of iodine
– may be seen when potassium iodide,
radiographic contrast medium, or
amiodarone

May occur in newborns when women
given large quantities of iodine
during pregnancy
Central Hypothyroidism
Due to hypothalamic or pituitary
disease
 May be associated with other
pituitary hormone deficiencies
 May precipitate adrenal crises if
thyroid hormone is replaced before
hydrocortisone

Clinical Features
Symptom
% Cases
Weakness
99
Dry skin
97%
Coarse skin
97%
Lethargy
91%
Slow speech
90%
Clinical Features
Symptom
% Cases
Edema of eyelids
90
Sensation of cold
89
Decreased sweating
89
Cold skin
83
Thick tongue
82
Clinical Features
Symptom
% Cases
Facial Edema
79
Coarseness of hair
76
Pallor of skin
67
Memory impairment
66
Constipation
61
Clinical Features
Symptom
% Cases
Weight gain
59
Hair loss
57
Pallor of lips
57
Dyspnea
55
Hoarseness
52
Cardiovascular
Cardiac output is decreased
 Peripheral vascular resistance is
increased
 Blood volume is reduced
 Elevated cholesterol
 Increased blood pressure
 Cardiomegaly
 Bradycardia

Alimentary System
Modest weight gain
 Decreased appetite
 Constipation

Nervous System
Essential for development of central
nervous system in fetus and
newborns
 Slowing of intellectual functions
 Psychiatric disorders
 Myxedema coma
 Hearing loss
 “hung-up reflexes”

Muscular/Skeletal System
Muscle aches and stiffness
 Increased muscle mass
 Growth failure in children
 Delayed maturation of bone

Fluids/Electrolytes
Decreased renal blood flow
 Delay in water excretion
 Hyponatremia

Hematopoietic System
Normocytic normochromic anemia
 High incidence of pernicious anemia
associated with hypothyroidism

Reproductive Function
Sexual immaturity
 Delayed or precocious puberty
 Galactorrhea
 Diminished libido
 menorrhagia

Laboratory
Free T4
 TSH
 Thyroid antibodies

– Thyroid peroxidase antibodies
(microsomal antibodies)
– Thyroglobulin antibodies
Radioactive T3
T4
TBG
Resin
Euthyroid
T4
TBG
Resin
Hypothyroid
T4 T3RU  TSH 
TBG
Resin
TBG Deficiency
T4 T3RU  TSH N
TBG
Resin
Primary Hypothyroidism
TSH
T4
TPO
Diagnosis
Increase
Decrease
+
Autoimm.
Increase
Decrease
-
Postsurg./
irradiation
TBG Deficiency
T4
T3RU
TSH
Dec.
Inc.
N
Treatment

Oral L-thyroxine therapy
– 5-10 ug/kg in newborns
– 1-2 ug/kg in adults