The adrenal glands and the gonads share a common embryological origin.
During the 5th and 6th week of the embryological development,
mesodermal cells from the posterior abdominal wall,
located between the root of the mesentery and the urogenital ridge,
proliferate and give rise to the adrenal cortex primordium.
By the 7th week of embryological development,
neural crest cells from the sympathetic ganglion migrate towards the center of the adrenal cortex primordium to form the adrenal medulla.
The gonads originated from the urogenital ridge.
At the beginning of the 5th week of the embryological development,
primordial germ cell migrate from the hindgut to the medial aspect of the urogenital ridge.
The urogenital ridge then enlongate caudally and growth in size to give rise to the gonads.
Diverse transcriptional factors,
endocrine markers and signaling pathways are required for the individualization and the differentiation of the adrenal glands and testis.
Although the etiology is not completely understood,
during this interrelated embryological developmental period,
some cells destined to become adrenocortical cells may nestle within the descending gonad.
Testicular adrenal rests tumors (TART) are benign lesions that develop due to overstimulation of the ectopic adrenal remnants within the testis.
They are commonly found in individuals with congenital adrenal hyperplasia (CAH).
Although the incidence of testicular adrenal rests varies in CAH,
it usually increase with age (might be found in up to 94% of the adults with CAH).
Testicular adrenal rests can be normally found in the testis and surrounding tissues in 5% to 15,0% of the newborns.
In normal individuals,
the testicular adrenal remnants become atrophic during development and are found in less than 1% of the normal adults.
Congenital Adrenal Hyperplasi (CAH)
CAH is a group of inheritable metabolic diseases that affect the adrenocortical steroid synthesis.
In most cases,
it is related to a defect of the CYP21A2 gene leading to 21-hydroxylase deficiency.
The result is insufficient production of cortisol by the adrenal cortex and,
in some cases,
also inadequate aldosterone synthesis.
the CAH is diagnosed at an early age soon after birth and the appropriate treatment has significantly reduced the morbidity and mortality.
the lack of the cortisol’ feedback to the hypothalamus nucleus and pituitary gland results in persistently elevated serum levels of the adrenocorticotrophic hormone (ACTH).
The chronically elevated ACTH levels stimulates the adrenal remnants in the testis to become hyperplasic.
Individuals with Addison’s disease,
Cushing’s and Nelson’s syndromes might also present TART.