Congenital hypothyroidism 
Incidence is around 1 out of 2500 live births.
All newborns with hypothyroidism are asymptomatic at birth, only few may exhibit some clues as follow...
1. Being less active than other babies. 
2. Muscles are softer 
3. Constipated
4. Cold and/or dry skin
5. Slow movements, may have hoarse cry.
6. May present as non- resolving Jaundice
7. Size appears larger for length.
8. May have large head, large tongue
9 . Difficult feeding
10. Bulging belly buttons.
Main effect is on brain development, late diagnosis results in poorer IQ.
It is the most common preventable cause of Mental Retardation.