First Glance

Fundamentals

a) Congenital Hypothyroidism
Causes :

Congenital Hypothyroidism
Transient	Permanent
Iodine deficiency	Thyroid dysgenesis
Iatrogenic	Maternal exposure to¹³¹ I
Maternal/neonatal	Dyshormonogenesis
Iodine deficiency maternal RAI therapy	Congenital toxoplasmosis
TSH receptor blocking antibodies	Hypothalamic pituitary disorders
Idiopathic

This type of hypothyroidism has been in existence since antiquity. This was portrayed in the ancient sculptures of goitrous dwarfs in 400 BC in South America. It was also described in writings about goitre in ancient Roman empire in the first century.
Congenital hypothyroidism presents at birth. It may be transient or permanent.

b) Cretinism

Severe iodine deficiency causing hypothyroidism in infancy and presenting as mental retardation, neurological maldevelopment and impaired growth is called cretinism. The infant having this form of hypothyroidism is called a cretin. It is rightly stated about a cretin that “What was supposed to be made into the image of God, has turned into an Imp”.

Epidemiology
Clinical manifestations

predominant neurological syndrome - which consists of disorders of stance and gait and disorders of hearing and speech.
predominant hypothyroidism and stunted growth

Prevention

Prevention of endemic cretinism with adequate correction of iodine deficiency.

c) Juvenile Hypothyroidism

Occurs in childhood and manifests mainly as growth retardation along with other generalised features of hypothyroidism

d) Adolescent Hypothyroidism

Hypothyroidism during adolescence presents with delayed puberty with/without short stature and menstrual irregularities in females.

Severity : Hypothyroidism is also classified on the basis of severity as

subclinical hypothyroidism
overt or frank hypothyroidism

a) Subclinical Hypothyroidism

In this, patients are asymptomatic and are identified in screening especially in patients at risk. Spontaneous subclinical hypothyroidism is more common in women and the incidence increases with age and is associated with the presence of antithyroid antibodies.

b) Overt or Frank Hypothyroidism

All causes of hypothyroidism can manifest with moderate to severe symptoms and signs. However, the clinical manifestations are variable and sometimes nonspecific too.

Risk Factors

The risk of hypothyroidism does not remain the same across entire population. It changes depending upon sex, age and with presence or absence of other autoimmune disorders.
The following is the list of such factors which will serve as needle of 'suspicion' and may help in early diagnosis as well as treatment of hypothyroidism.

Past history of thyroid / pituitary / hypothalamic disease
Family history of thyroid disease
Elderly individuals
History of hyperlipidaemia
History of depression
Obesity
History of drug intake e.g. amiodarone, iodine, lithium carbonate, para-aminosalicilic acid
- history of other autoimmune diseases in the patients or in the family
- insulin dependent diabetes mellitus
- primary adrenal insufficiency
- pernicious anaemia
- vitiligo
- malabsorption syndromes
- collagen vascular disorders
History of thyroid surgery
History of RAI ¹³¹ treatment for thyrotoxicosis
History of head and neck irradiation
History of postpartum thyroid dysfunction
Down syndrome
Short stature

These patients need to be screened for the presence of hypothyroidism. Clinical features discussed in the next section along with diagnostic criteria are to be utilised for confirmation of hypothyroidism.

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