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55. What are the causes of testicular enlargement in a boy with CAH due to
    21 α-hydroxylase defi ciency?

Bilateral symmetrical testicular enlargement in a boy with CAH due

21 α-hydroxylase defi ciency suggests reactivation of hypothalamo–pituitary–

testicular axis (either as a part of GDPP due to delayed initiation of therapy or

normal puberty), whereas unilateral/asymmetrical testicular enlargement sug-

gests the development of testicular adrenal rest tumor.

56. What is testicular adrenal rest tumor?

In a developing embryo, adrenogonadal primordium differentiates into adrenal

and gonadal tissue. During differentiation, few adrenal cells are admixed with

gonadal tissue and are termed as “adrenal rest cells.” Despite ectopic location,

these cells retain the characteristics of adrenal tissue including responsiveness

to ACTH. Therefore, in the presence of ACTH excess these adrenal rest cells

may proliferate leading to adrenal rest cells tumor in testes (TART) and ovary

(OART). Although CAH is the most common cause of TART, it may be seen in

any disorder associated with ACTH excess, e.g., primary adrenal insuffi ciency,

ACTH-dependent Cushing’s syndrome and Nelson’s syndrome (Fig. 10.14 ).

Urogenital ridge

Adrenogonadal

Kidney primordium

Neural

crest cells

Fetal

adrenal

Cortex

Medulla

Adult

adrenal

Ovary Testis

Bipotential

gonad

Primordial

germ cells

Fig. 10.14 Embryogenesis of adrenals, gonads and adrenal rest cells in gonads

10 Congenital Adrenal Hyperplasia