Published online by Cambridge University Press: 15 February 2010
Clinical presentation
Micropenis:
Incidental finding on newborn examination.
Finding on examination of an hypoglycaemic baby.
Definition
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
History:
Family history of ambiguous genitalia.
Ethnic origin.
Examination:
Dysmorphism.
Midline defects: hypertelorism, cleft palate.
Ophthalmic examination: Optic nerve hypoplasia/septo-optic dysplasia.
Symptoms/signs hypothalamic–pituitary hormone deficiencies (see Chapter 7).
Differential diagnosis
Normal variant.
Anterior pituitary hormone deficiency.
Ambiguous genitalia (see Chapter 8).
Syndromes, such as CHARGE association, Prader–Willi syndrome.
Investigations
Investigate as for hypopituitarism (see Chapter 7).
It is essential to do pre-feed blood sugars until normal and stable.
Temperature.
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.
Karyotype.
Genetics opinion.
Investigate as for ambiguous genitalia if appropriate (see Chapter 8).
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