Dihydrotestosterone and dihydrotestosterone/ratio may be used for differential diagnosis of diseases of sexual differentiation (DSD)

Gold serum separator (SST) tube

Immediately following collection, thoroughly mix sample by gently inverting 5 times

1. Allow sample to clot for a minimum of 30 minutes
2. Spin within one (1) hour of collection
3. Transfer serum to a Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp), labelled as serum
4. Freeze

Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp)

Red serum vial/tube - 5 mL

Lavender (EDTA), 4mL

Dk green heparin (Li or Na), no gel

Lavender/Dk green:

Immediately following collection, mix sample thoroughly by gentle inverting 8 - 10 times, to prevent clotting

Red: 

1. Allow sample to clot
2. Spin within one (1) hour of collection
3. Transfer serum to a Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp), labelled as serum
4. Freeze

Lavender/Dk green:

1. Spin within one (1) hour of collection
2. Transfer plasma to a Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp), labelled as the appropriate plasma type
3. Freeze

Frozen (preferred) - 19 months

Freeze/thaw cycles - stable x 6

Refrigerated - 7 days

Ambient - 7 days

High performance liquid chromatography (HPLC) with Tandem Mass Spectrometry

ng/dL

DHT levels may be inappropriately low compared to testosterone levels in 5a-reductase deficiency. It is recommended by guidelines to measure the ratio of testosterone to DHT. DHT levels may also be monitored to follow the effectiveness of 5a-reductase inhibitor testament in female alopecia.