Growth hormone (GH) is normally secreted in a highly episodic fashion in animals and humans. Although it has become clear that both the amount of GH secreted and the pattern in which it is secreted are important for its actions (1, 2), it is not yet understood how such a closely controlled temporal pattern of GH release is achieved. Pituitary hormone secretion represents the ‘motor’responses of hypothalamic neuronal systems, and both the amount of GH secreted and the pattern of its release are signalling elements from the CNS to the periphery via the endocrine hypothalamus.

Much has been written about the measurement of GH secretory blood profiles, and deductions have been made about secretory rates, how GH secretion varies under different physiological conditions, and how the pattern of GH exposure is important, not only for growth (3, 4), but also for the appropriate expression of a wide variety of metabolic enzymes (5, 6). This article concentrates on a less accessible aspect of this topic, the properties that might be shown by the neural systems involved in control of the GH rhythm. As episodic secretion is the rule rather than the exception in hypothalamo-pituitary endocrine systems, it may be helpful to consider what is known about another neuroendocrine system in which pulsatile secretion has been examined at the neural level.