What is secondary hypothyroidism?

Caused by TSH deficiency, 1% of hypothyroid, causes may be hypopituitarism or others (pituitary tumor, postpartum necrosis (Sheehan), hypophysitis, non-pituitary tumor (craniopharyngioma), infiltrative diseases, inactivation mutation of TSH or TSH receptor) may be isolated TSH deficiency, but more often related w/other hormone deficiency.