Published online by Cambridge University Press: 15 February 2010
Incidental finding on newborn examination.
Finding on examination of an hypoglycaemic baby.
Penile size: measured from the pubic tubercle to tip of the stretched penis in a term baby is usually >3 cm. Micropenis is a measurement <2.2–2.5 cm (varies with ethnicity).
In the preterm baby the normal penile length (cm) is 2.27 + 0.16 GA, where GA is the gestational age in weeks.
Approach to the problem
Family history of ambiguous genitalia.
Midline defects: hypertelorism, cleft palate.
Ophthalmic examination: Optic nerve hypoplasia/septo-optic dysplasia.
Symptoms/signs hypothalamic–pituitary hormone deficiencies (see Chapter 7).
Anterior pituitary hormone deficiency.
Ambiguous genitalia (see Chapter 8).
Syndromes, such as CHARGE association, Prader–Willi syndrome.
Investigate as for hypopituitarism (see Chapter 7).
It is essential to do pre-feed blood sugars until normal and stable.
Ultrasound of head for midline defects.
Anterior pituitary hormone levels:
– Adrenocorticotrophic hormone (ACTH) and cortisol.
– Growth hormone (GH) (insulin-like growth factor (IGF-I), insulin-like growth factor binding protein-3 (IGFBP3)).
– Luteinizing hormone (LH) and follicle stimulating hormone (FSH).
– Thyroid-stimulating hormone (TSH) and free thyroxine (fT4).
Magentic resonance imaging (MRI) of the head.
Investigate as for ambiguous genitalia if appropriate (see Chapter 8).