Congenital secondary hypothyroidism with low serum GH and prolactin levels in a 27-day-old male infant.

A male infant with secondary hypothyroidism is described. Within the first month after birth, the patient manifested feeding difficulties, lethargy, persistent jaundice, umbilical hernia, and large anterior and open posterior fontanels. The roentgenogram of the knee joints at 27 days showed absence of the distal femoral epiphyses. His serum thyroid-stimulating hormone (TSH) level was low despite decreased levels of triiodothyronine (T3) and tetraiodothyronine (T4) in serum. Assessment of the hypothalamic-pituitary hormone (TRH) nor growth hormone (GH) responses to L-arginine and insulin, while responses of both luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to luteinizing hormone-releasing hormone (LH-RH) and adrenocorticotropic hormone (ACTH) to insulin were within normal limits. The malady of the patient in this case was not detected by newborn screening for congenital hypothyroidism due to the fact that in the Aomori district of Japan thyroid screening involves only the measurement of TSH. Such measurement cannot detect cases of secondary or tertiary hypothyroidism such as our patient. Replacement therapy was initiated at 58 days and his physical and mental development has been regarded as normal since treatment.