Endocrine Abstracts

Background: A variety of preparations for testosterone replacement therapy are currently available. Testogel, a transdermal gel, is widely used and considered one of the most convenient. However, a wide variation in the increment of serum testosterone two hours after its application has been reported.

Aim: To investigate whether skin thickness affects the absorption of testogel.

Subjects and methods: Fourteen patients (mean age 55.4 years, range 19–75 years) diagnosed with hypogonadism (mean year 2000, range 1985–2006), seven of which had acromegaly, (3 cured, 4 not cured) were studied. All were using testogel 50 mg daily. About 22–24 h following previous day gel application blood samples for serum testosterone were taken (between 0900 and 1000 h). The timing of sampling was prior to the gel being applied (time 0), 2 h after application of the gel (time 120) and 4 h after application (time 240). Gel was applied to either top of arm or back of shoulder. Skin fold thickness was measured using skin fold calipers on the back of the hand (mean 3.1, range 2–5).

Results: Mean serum testosterone at time 0 was 10.51 nmol/l (4.6–21.3), at time 120 was 13.47 nmol/l (5.6–26.3) and at time 240 was 18.59 nmol/l (8.3–42.9). There was significant correlation between serum testosterone at time 0 and % increase at time 240 (P=0.03). There was no significant correlation between skin fold thickness and the % increase of serum testosterone at time 240(P=0.8). The increment in serum testosterone at time 240 in patients with acromegaly was not significantly different with the one observed in patients without acromegaly (matched for BMI and serum testosterone at time 0).

Conclusion: Serum testosterone levels at time 240 is not correlated by skin thickness following application of testogel. Therefore this preparation could be considered as a form of testosterone replacement therapy for patients with thicker skin as a result of acromegaly.