A 3-week-old boy is brought with persistent jaundice, poor weight gain and two episodes of jitteriness before feeds. He was born at term with a small penis and testes that were not palpable in the scrotum. Examination shows a sleepy infant with no hepatosplenomegaly; the serum free thyroxine is low, while the thyroid-stimulating hormone concentration is not increased. Which one of the following is the most likely diagnosis?