[OA] Hypogonadism with Normal Serum Testosterone
Questions To Consider
1. What are the criteria for LOH?
2. What are the pitfalls of measuring serum total testosterone concentration?
3. What common conditions cause increased SHBG?
4. What methods should be used to determine FT and bioT?
A 69-year-old man was referred to the endocrine clinic with a 3-year history of erectile dysfunction, reduced libido, and lack of nocturnal tumescence with no response to phosphodiesterase type 5 inhibitors (sildenafil and tadalafil). The symptoms troubled him to such an extent that he asked his general practitioner to be referred to a specialist clinic.
On examination he was 178 cm tall and obese [body mass index (BMI) 37.3 kg/m2]. His arm-span-to-height ratio was <1.05 and his cardiovascular examination did not reveal heart murmurs. He had a normal hair pattern and no gynecomastia. Testicular volume was reduced bilaterally at 12–15 mL (reference interval ≥15 mL).
Testosterone, measured by a 1-step chemiluminescent immunoassay (Abbott Architect, second generation testosterone assay) was 16.0 nmol/L (reference interval 4.9–32 nmol/L); his sex hormone–binding globulin (SHBG)3 was increased at 153 nmol/L (13.5–71.4 nmol/L) as were luteinizing hormone (LH) and follicle-stimulating hormone (FSH) at 33.4 IU/L (0.6–12.0 IU/L) and 54.7 IU/L (1.0–11.9 IU/L), respectively (Table 1).
These results, which indicated hypergonadotropic hypogonadism, were confirmed on repeated testing 3 weeks later.
At that time, testosterone was also measured by LC-MS/MS and the results confirmed a normal total testosterone, thus excluding a positive immunoassay interference. Low calculated values of bioavailable testosterone (bioT) [2.05 nmol/L (2.29–14.5 nmol/L)] and free testosterone (FT) [0.106 nmol/L (0.174–0.729 nmol/L)] were consistent with hypogonadism.
Further blood tests showed normal results for the routine metabolic panel, complete blood count, transferrin saturation, estrogen, thyroid tests, and prolactin. Plasma glucose, adjusted calcium, vitamin B12, and morning cortisol results were also unremarkable, making an autoimmune condition unlikely.
Borovickova I, Adelson N, Viswanath A, Gama R. Hypogonadism with Normal Serum Testosterone. Clin Chem 2017;63(8):1326-9. Hypogonadism with Normal Serum Testosterone | Clinical Chemistry
Questions To Consider
1. What are the criteria for LOH?
2. What are the pitfalls of measuring serum total testosterone concentration?
3. What common conditions cause increased SHBG?
4. What methods should be used to determine FT and bioT?
A 69-year-old man was referred to the endocrine clinic with a 3-year history of erectile dysfunction, reduced libido, and lack of nocturnal tumescence with no response to phosphodiesterase type 5 inhibitors (sildenafil and tadalafil). The symptoms troubled him to such an extent that he asked his general practitioner to be referred to a specialist clinic.
On examination he was 178 cm tall and obese [body mass index (BMI) 37.3 kg/m2]. His arm-span-to-height ratio was <1.05 and his cardiovascular examination did not reveal heart murmurs. He had a normal hair pattern and no gynecomastia. Testicular volume was reduced bilaterally at 12–15 mL (reference interval ≥15 mL).
Testosterone, measured by a 1-step chemiluminescent immunoassay (Abbott Architect, second generation testosterone assay) was 16.0 nmol/L (reference interval 4.9–32 nmol/L); his sex hormone–binding globulin (SHBG)3 was increased at 153 nmol/L (13.5–71.4 nmol/L) as were luteinizing hormone (LH) and follicle-stimulating hormone (FSH) at 33.4 IU/L (0.6–12.0 IU/L) and 54.7 IU/L (1.0–11.9 IU/L), respectively (Table 1).
These results, which indicated hypergonadotropic hypogonadism, were confirmed on repeated testing 3 weeks later.
At that time, testosterone was also measured by LC-MS/MS and the results confirmed a normal total testosterone, thus excluding a positive immunoassay interference. Low calculated values of bioavailable testosterone (bioT) [2.05 nmol/L (2.29–14.5 nmol/L)] and free testosterone (FT) [0.106 nmol/L (0.174–0.729 nmol/L)] were consistent with hypogonadism.
Further blood tests showed normal results for the routine metabolic panel, complete blood count, transferrin saturation, estrogen, thyroid tests, and prolactin. Plasma glucose, adjusted calcium, vitamin B12, and morning cortisol results were also unremarkable, making an autoimmune condition unlikely.
Borovickova I, Adelson N, Viswanath A, Gama R. Hypogonadism with Normal Serum Testosterone. Clin Chem 2017;63(8):1326-9. Hypogonadism with Normal Serum Testosterone | Clinical Chemistry
