The etiology of hypergonadotropism in azoospermic patients has been well studied and is known to involve a negative feedback mechanism involving Sertoli cells and inhibin B[
14]. Serum FSH can increase to as high as two to four fold the normal range. Although FSH can facilitate the initiation of spermatogenesis in pubertal males, hypogonadal men still can demonstrate fertility in the absence of FSH. Only the combination of FSH and testosterone can support a qualitatively and quantitatively full normal level of spermatogenesis.
In patients with obstructive azoospermia, if reconstructive surgery fails or is not feasible, microscopic epididymal sperm aspiration (MESA) or testicular sperm extraction (TESE) is the method of choice for recovering spermatozoa for
in vitro fertilization (IVF). In patients with non-obstructive azoospermia, TESE is the method of choice for recovering spermatozoa as a male therapeutic approach in ICSI. Due to the psychological, economic, or physical burden of the IVF procedure, useful criteria to predict the absence of spermatozoa are highly important for making a decision of sperm retrieval procedure. Although histopathology has been found to be the best method for predicting successful sperm recovery in non-obstructive azoospermic patients, this method requires an operative procedure[
5,
15]. Several non-invasive laboratory tools have been suggested for prediction of the presence of spermatozoa, such as the levels of inhibin B and FSH in serum. Inhibin B level is a parameter that has been shown to be associated with maturation arrest; however, it is not used routinely and is not diagnostic[
16,
17]. The combination of inhibin B and FSH levels has been reported to be a better predictor for the presence of sperm in TESE. However, the prediction is not absolutely reliable[
18]. FSH has been used as a marker of spermatogenesis, but the optimal criterion for serum level has still not been precisely determined[
5]. A two-fold increase above the upper limit of normal serum FSH level has usually been used as the cut-off value for spermatogenesis, but this does not provide a better predictive rate than histopathology[
19]. It has been reported that when elevated plasma levels of FSH are three fold above the normal limit (more than 27 mIU/mL) this precludes, with a probability of 95%, the existence of full spermatogenesis[
20]. However, with regard to FSH plasma levels, a high FSH level can not be used for the diagnosis of spermatogenic maturation arrest and Sertoli-cell-only syndrome[
20].
The predictive power for detecting oligospermia among men with FSH above 10 IU/L has been found to be 100%[
5]. In a study of 106 azoospermic patients, small testicular size (< 4 cm) and elevated FSH (> 10) was associated with a decrease in the success rate of sperm retrieval rate from 77% to 29%[
21]. In another report it was found that a level above 60 mIU/mL of serum FSH could completely exclude the possibility of sperm retrieval from testis; the sperm retrieval rate was 100% for FSH ≤15 mIU/mL [
22]. Although measurement of serum FSH is a non-invasive test for predicting success rate of sperm retrieval in azoospermic patients, the cut-off value for FSH for predicting spermatogenesis is rather variable. We suggest that one major reason for the variability is due to the development of microsurgical testicular sperm retrieval (microTESE). The microTESE has better sperm retrieval rate than random testicular biopsy. Many men who have been diagnosed with non-obstructive azoospermia either due to the pathological conditions known as hypospermatogenesis or Sertoli-cell only syndrome have been found to have foci of sperm production within the testicles. This observation has revolutionized an old concept that the testis produced sperm in a uniform fashion and has lead to the new concept of focal spermatogenesis. In our study, we found that a low FSH level (< 19.4 mIU/mL) is not a predictive criterion for success sperm retrieval. A comprehensive diagnostic evaluation and reconstructive operative procedure are indicated for azoospermic men with a low FSH level (< 19.4 mIU/mL). But men with elevated FSH (> 19.4 mIU/mL) would benefit from a cut-off value for FSH to predict the failure for sperm retrieval. This is very important for microTESE, because fresh testicular sperm will be needed to approve patients for successful concomitant IVF and ICSI procedures.