Hypothyroidism is a condition in which the thyroid gland doesn't produce enough thyroid hormone. Hypothyroidism's deficiency of thyroid hormones can disrupt such things as heart rate, body temperature and all aspects of metabolism. Hypothyroidism is most prevalent in older women. Major symptoms include fatigue, cold sensitivity, constipation, dry skin and unexplained weight gain. Treatment consists of thyroid hormone replacement.

1. HYPOTHYROIDISM
Dr. Chavan P. R

2. DEFINITION
 A condition in which the thyroid gland
doesn't produce enough thyroid
hormone.
 Also called as underactive thyroid

4. PATHOPHYSIOLOGY
 The vast majority of hypothyroid patients have thyroid
gland failure (primary hypothyroidism).
 The causes include chronic autoimmune thyroiditis
(Hashimoto’s disease), iatrogenic hypothyroidism, iodine
deficiency, enzyme defects, thyroid hypoplasia, and
goitrogens.
 Pituitary failure (secondary hypothyroidism) is an
uncommon cause resulting from pituitary tumors, surgical
therapy, external pituitary radiation, postpartum pituitary
necrosis, metastatic tumors, tuberculosis, histiocytosis,
and autoimmune mechanisms.

6. CLINICAL PRESENTATIONs

7. DIAGNOSIS
 A rise in the TSH level is the first evidence of primary
hypothyroidism.
 Many patients have a free T4 level within the normal
range (compensated hypothyroidism) and few, if any,
symptoms of hypothyroidism.
 As the disease progresses, the free T4 concentration
drops below the normal level.
 The T3 concentration is often maintained in the
normal range despite a low T4.

9.  Antithyroid peroxidase antibodies and
antithyroglobulin antibodies are likely to be elevated.
 The RAIU is not a useful test in the evaluation of
hypothyroidism because it can be low, normal, or
even elevated.
 Pituitary failure (secondary hypothyroidism) should
be suspected in a patient with decreased levels of
T4 and inappropriately normal or low TSH levels.

10. DESIRED OUTCOMES
 To normalize thyroid hormone concentrations in
tissue
 Provide symptomatic relief,
 Prevent neurologic deficits in newborns and children,
and
 Reverse the biochemical abnormalities of
hypothyroidism.

11. NONPHARMACOLOGIC TREATMENT

13. TREATMENT CHART

14. PHARMACOLOGIC TREATMENT
 Levothyroxine (L-thyroxine, T4) is the drug of choice
for thyroid hormone replacement and suppressive
therapy because it is chemically stable, relatively
inexpensive, free of antigenicity, and has uniform
 Because T3 (and not T4) is the biologically active
form, levothyroxine administration results in a pool of
thyroid hormone that is readily and consistently
converted to T3.

15.  Young patients with long-standing disease and
patients older than 45 years without known cardiac
disease should be started on 50 mcg daily of
levothyroxine and increased to 100 mcg daily after 1
month.
 The recommended initial daily dose for older patients
or those with known cardiac disease is 25 mcg/day
titrated upward in increments of 25 mcg at monthly
intervals to prevent stress on the cardiovascular
system

16.  The average maintenance dose for most adults is
about 125 mcg/day, but there is a wide range of
replacement doses, necessitating individualized
therapy and appropriate monitoring to determine an
appropriate dose.
 Patients with subclinical hypothyroidism and marked
elevations in TSH (greater than 10 milli-international
units per liter [mIU/L]) and high titers of TSAb or prior
treatment with sodium iodide 131 may benefit from
treatment with levothyroxine.

17.  Levothyroxine is the drug of choice for pregnant women,
and the objective of the treatment is to decrease TSH to
1 mIU/L and to maintain free T4 concentrations in the
normal range.
 Cholestyramine, calcium carbonate, sucralfate, aluminum
hydroxide, ferrous sulfate, soybean formula, and dietary
fiber supplements may impair the absorption of
levothyroxine from the GI tract.
 Drugs that increase nondeiodinative T4 clearance include
rifampin, carbamazepine, and possibly phenytoin.
Amiodarone may block the conversion of T4 to T3.

18.  Thyroid, USP (or desiccated thyroid) is derived from
hog, beef, or sheep thyroid gland. It may be
antigenic in allergic or sensitive patients.
Inexpensive generic brands may not be
bioequivalent.
 Thyroglobulin is a purified hog-gland extract that is
standardized biologically to give a T4:T3 ratio of
2.5:1. It has no clinical advantages and is not widely
used.

19.  Liothyronine (synthetic T3) has uniform potency but
has a higher incidence of cardiac adverse effects,
higher cost, and difficulty in monitoring with
conventional laboratory tests.
 Liotrix (synthetic T4:T3 in a 4:1 ratio) is chemically
stable, pure, and has a predictable potency but is
expensive. It lacks therapeutic rationale because
about 35% of T4 is converted to T3 peripherally.

20.  Excessive doses of thyroid hormone may lead to
heart failure, angina pectoris, and myocardial
infarction.
 Allergic or idiosyncratic reactions can occur with the
natural animal-derived products such as desiccated
thyroid and thyroglobulin, but they are extremely rare
with the synthetic products used today.
 Excess exogenous thyroid hormone may reduce
bone density and increase the risk of fracture.

21. EVALUATION OF THERAPEUTIC
OUTCOMES
 Serum TSH concentration is the most sensitive and specific monitoring
parameter for adjustment of levothyroxine dose. Concentrations begin
to fall within hours and are usually normalized within 2 to 6 weeks.
 TSH and T4 concentrations should both be checked every 6 weeks
until a euthyroid state is achieved. An elevated TSH level indicates
insufficient replacement.
 Serum T4 concentrations can be useful in detecting noncompliance,
malabsorption, or changes in levothyroxine product bioequivalence.
TSH may also be used to help identify noncompliance.
 In patients with hypothyroidism caused by hypothalamic or pituitary
failure, alleviation of the clinical syndrome and restoration of serum T4
to the normal range are the only criteria available for estimating the
appropriate replacement dose of levothyroxine.

22. Thank you