SEX HORMONE BINDING PROTEIN (SBP) AS A MARKEh OF ANDROGEN SENSITIVITY IN INFANTS AND CHILDREN

Abstract

Establishing a reliable test of androgen sensitivity is still prerequisite for etiological diagnosis in infants suspected of androgen insensitivity syndrome (AIS). Since androgens are known to decrease SBP levels we have investigated the possibility of using plasma SBP as a marker of androgen sensitivity, and studied the conditions for a rational protocol. The ontogenic pattern of SBP from birth to adulthood was first established in 695 controls, (by a solid phase method). SBP levels (μg/l) low at birth, (6.3±3) rise to 22.3±7.5 during the first month of life correlatively with time, with no sex difference but large individual variations. In addition, SBP decreased significantly after either an acute or a 3-day routine ACTH test. Whatever the age (1 mo-13 yr ), SBP levels decreased significantly (mean=30%) in a group of 40 boys at the end (day 14) of an hCG test (1500 IU/48 h × 7), but the response was very variable and not correlated with testosterone levels. In contrast, the exogenous administration of fluoxymesterone (10 mg/m²/d.x 10 d.) or depo-testosterone (4 IM injections of 100 mg/m² every 2 weeks) induced a siginificant drop (mean 2 fold) in 10 infants with idiopathic male pseudohermaphroditism, but not in 2 suspected of AIS.

In conclusion. SBP appears a good marker of androgen sensitivity in infancy, however establishing a protocol requires three conditions: 1) the test should not be done during the 1st month of life (rising basal levels), 2) neither after an ACTH test and 3) utilise the exogenous administration of a high dose of androgens for somewhat a prolonged period of time.

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