Common presentations of Juvenile Hypothyroidism –
Features of juvenile (congenital) hypothyroidism are :

Open posterior fontanel and wide sutures
Large tongue → Can cause respiratory difficulties
Rough dry skin which is cool & mottled
Hypotonia, large abdomen, flaccid muscles
Sleepy, little cry, poor feed & chocking spells during feeding.
Short neck with a thick supraclavicular pad of fat may be present. 
Marked physical & mental retardation, delayed social smile.
Short stature, normal head size with short extremities.
Delayed relaxation of deep tendon reflexes.
An umbilical hernia
Edematous, characteristic facies
Constipation
Pallor, hypothermia
Sexual precocity occasionally
Refractory anaemia common
Delayed dentition
Open mouth with protuberant tongue
Slow pulse, cardiomegaly & Heart murmur.
Prolongation of physiological jaundice due to delayed maturation of glucuronide conjugation.

Clinical features of acquired hypothyroidism 

Growth retardation
Disproportionately large head and trunk as compared to limbs
Increased upper and lower body segment ratio
Gross mental retardation is not usually present
Delayed skeletal maturation
Delayed dental development
Puffy face
Lethargy
Cold intolerance
Delayed puberty
Myopathy
Pseudotumor cerebri

Note: In congenital hypothyroidism there is hypotonia. Rarely the muscle may appear hypertrophied (pseudohypertrophy) with an athletic appearance → Kocher-Debre-Semelaigne syndrome gives infant Hercules appearance.
Growth retardation
Mental ratardation within 2 years
Umbilical Hernia
All of these