Ar Ar

AD X-linked

Absent Decreased

Decreased Decreased

Often temporary Complete GH-1 deletion Present Partial GH-1 deletions,

GHRH receptor mutations Present Partial GH-1 mutations

Present X-chromosome deletions or duplications

AR, Autosomal recessive; AD, Autosomal dominant.

Table 2 Elements of GH Axis

Hypothalamus

Growth hormone releasing hormone Somatostatin

? Growth hormone secretagogue Pituitary

*Growth hormone releasing hormone receptor *Pituitary transcription factors (Rpx, PROP, Pit-1) *Growth hormone

? Growth hormone secretagogue receptor Target tissues

*Growth hormone receptor *Insulin-like growth factor 1 (IGF-1) *IGF-1 receptor IGF-binding proteins

*Indicates defect in this element described in humans.

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