Testosterone explained

The principal male sex hormone, made mainly in the testes. It governs libido, muscle and bone mass, red cell production, energy and mood, and falls gradually with age. The sample should be taken in the morning, and a low result confirmed on a second test before it means anything — the Endocrine Society guideline is explicit on both points. Low, with symptoms: Explains a cluster easily blamed on stress or ageing: low libido, erectile difficulty, tiredness, loss of muscle, low mood and poor concentration.

Fasting: Not required. Best time: Morning, ideally between 7am and 10am, when levels peak. A sample taken later in the day can read low in a man whose level is normal — which is why the appointment time matters here more than for most tests.

Commonly: the time of day the sample was taken; weight, as body fat lowers testosterone; poor sleep and sleep apnoea; acute illness, which lowers it temporarily; steroids and some prescribed medicines. A single result is not a diagnosis. Values are read against the laboratory's own reference range and alongside your history, your symptoms and the rest of the panel — which is why every package includes a doctor to go through them with you.

At Smart Care Polyclinic, 29 Doha Centre, Al Maktoum Rd, Deira, Dubai. It is included in the Smart Extra Health, the Hair Loss Panel, the Well Man Panel, or it can be ordered on its own. Walk in during opening hours or call +971 (0)4 379 3562.