Among the diurnal variation list, which hormone is higher in the PM period?

• A. Growth hormone
• B. Prolactin
• C. Cortisol
• D. Iron

Answer: (A)

Growth hormone has a strong nocturnal pulse pattern tied to sleep. The body releases GH mainly during sleep, with the largest bursts occurring in the early part of the night when deep sleep dominates. Because of this, GH levels are higher in the evening/night (the PM period) than during the day. Cortisol, on the other hand, rises in the morning upon waking and falls through the day, so it isn’t higher in the PM. Prolactin does increase during sleep as well, but the most pronounced nocturnal surge among these is growth hormone. Iron is not a hormone and doesn’t follow this diurnal hormonal rhythm.