Pituitary Hormone Panels and Imaging

The pituitary is not a set of independent laboratory values. It is a control centre that signals target glands, so results must be read in pairs: - TSH with free T4 - ACTH with cortisol - LH and FSH with testosterone or estradiol - Growth hormone with IGF-1 A trophic hormone can look “normal” yet be abnormal for the clinical situation. If free T4 is low, a normal TSH is not reassuring; the pituitary should be responding with a high TSH. A normal or low TSH beside low free T4 is therefore inappropriately low and points toward central hypothyroidism. This pattern is the central skill in pituitary interpretation: ask whether the pituitary response fits the target-gland result. Primary gland failure produces a high trophic hormone because the pituitary is trying to stimulate a failing gland. Pituitary or hypothalamic failure produces a low, normal, or inadequately elevated trophic hormone because the signal itself is impaired. Prolactin works differently. Dopamine from the hypothalamus normally suppresses prolactin release. A stalk lesion can interrupt dopamine delivery and cause a mild prolactin rise even when...