Title: Understanding Hypothyroidism in Adults: Pathogenesis, Etiology, Clinical Features, Diagnosis, and Treatment of Myxedema Introduction: Hypothyroidism is a common endocrine disorder characterized by decreased thyroid hormone production, leading to various systemic manifestations. Myxedema represents severe hypothyroidism with distinctive clinical features and requires prompt diagnosis and management. Pathogenesis: Hypothyroidism typically arises from primary thyroid gland dysfunction, autoimmune thyroiditis (Hashimoto's thyroiditis) being the most common cause worldwide. Other etiologies include iatrogenic causes (e.g., thyroidectomy, radioiodine therapy), iodine deficiency, congenital defects, and certain medications.

1. Dr. Merin Emanuel K

2. By the end of this lecture, the
students will be able to:
 Understand the pathologic mechanism of
hypothyoidism in terms of:
 Myxedema
 Hashimoto’s disease
 Etiology
 Clincal Features
 Diagnosis
 Treatment

3. DEFINITION
Hypothyroidism is a clinical syndrome caused
by low levels of circulating thyroid hormones.In
adults, it is usually known as myxedema.

4. ETIOLOGY
According to causes it is divided into:
 Primary
 Secondary

5. Primary Hypothyroidism
 Autoimmune hypothyroidism: for example
Hashimoto’s thyroiditis, atropic thyroiditis.
 Iatrogenic: Excess use of radioiodine (131I),
thyoidectomy, external irradication of neck for
lymphoma or cancer
 Iodine deficiency : dietary intake below
50microgram per day

6.  Drugs: Excess of iodine(Wolff-Chaikoff effect),
excess use of antithyroid drugs, lithium, p –
aminosalicylic acid and other cytokines.
 Congenital hypothyroidism.

7. Secondary Hypothyroidism
 Pituitary hypothyoidism: Pituitary resection,
pituitary tumors affecting thyotrophs, and
Sheehan’s syndrome(post partum necrosis of
pituitary).Hypothyrotdism occurs due to
decreased TSH secretion.

8.  Hypothalamic hypothyroidism: Brain injury
involving hypothalamus, tumors,in which
secretion of TRH is less.
 Thyroid hormone resistance: Features of
hypometabolism similar to hypothyroidism
could occur due to resistance of peripheral
tissues to thyroid hormones

9. CLINICAL FEATURES
 General features: Tiredness, weight gain without
an appreciable increase in caloric intake ( due to
lower than normal metabolic rate), intolerance to
cold.
 Cardiovascular features: Decreased adrenergic
activity causing bradycardia.
 Hematological features: Anemia

10.  Neuromuscular features: Sleepliness, delayed
relaxation of ankle jerks, aches and pain, carpel
tunnel syndrome( due to entrapment in excess
ground substance.)
 Dermatological features: Dry thick skin, sparse hair,
non – pitting edema due to infiltration.
 Reproductive features: Menorrhagia, infertility,
impotence(less common), galactorrhoea.
 Gastrointestinal features: Constipation

11. SIGNS
 Dry coarse skin
 Puffy face and limbs
 Myxedema
 Diffuse alopecia
 Bradycardia
 Peripheral edema
 Delayed tendon
reflex relaxation
 Carpel tunnel
syndrome
SYMPTOMS
 Tiredness, weakness
 Dyspnea
 Paresthesia
 Difficulty to
concentrate and poor
memory
 Constipation
 Weight gain with
poor appetite
 Menorrhagia

12. DIAGNOSIS
 Serum T3 and T4 levels low.
 Serum TSH levels high in primary and low in
secondary
 Serum cholestrol high
 Peripheral blood film macrocytic anaemia
 Photomotogram – delayed ankle jerk.

13. HASHIMOTO’S THYROIDITIS
 It is a chronic form of autoimmune thyroiditis
in which antibodies are formed against the
thyroglobulin and thyoid peroxidase.
Therefore, thyroid cells are damaged and
hypothyroidism develops.

14. TREATMENT
 Thyroid hormone replacement is the mainstay of
treatment.
 T4 intituted at a dose of usually 10 to 15 microgm
per kg per day to maintain its normal level in
plasma.
 T3 is not needed. Giving T3 raises plasma T3 to
unphysiologic levels.

15. THANK YOU