TSH level in men

This test measures the hormone TSH circulating in your blood. Your pituitary makes TSH and sets the pace of the thyroid. The thyroid then produces T4 and T3, the hormones that keep your metabolism up to pace.

The feedback is log-linear. A small fall in free T4 produces a much larger rise in TSH. That makes this the most sensitive first test.

The direction is counter-intuitive. If the thyroid runs slow, the pituitary pulls harder and the number climbs. With too much hormone the signal switches off instead. So a high value means an underactive thyroid. With an overactive one the number sits low.

For men the link with the sex hormones is the most interesting part. The thyroid also drives the binding protein SHBG. With an overactive thyroid SHBG rises, so more of your testosterone becomes bound. Your total testosterone can then look normal while the free fraction disappoints. With an underactive thyroid the reverse often happens.

That is the practical reason to measure both. Disappointing energy alongside a perfectly good testosterone is a classic reason to add free T4.

Men who investigate energy, libido or body composition almost always start with testosterone. That is logical, but it leaves a common explanation on the table. An underactive thyroid produces nearly the same pattern of complaints.

Fatigue, less interest in sex, slower recovery, cold hands and slowly climbing weight fit both. If only testosterone is measured and it is normal, the question stays unanswered.

One misunderstanding deserves emphasis. Many men read a low value as favourable, as though the thyroid were then running efficiently. The opposite is true. A lowered TSH usually means the thyroid makes too much hormone. That comes with a high resting heart rate, poor sleep and loss of muscle mass. For strength and recovery that is unfavourable.

Sleep debt and chronic stress belong in this story too. They shift the daily rhythm of TSH and disturb your testosterone at the same time. A single measurement during a bad stretch is therefore worth little.

Have TSH measured when energy, libido or recovery structurally disappoint. That applies particularly when your testosterone has already been measured and came back normal. The thyroid is then the most obvious next step.

Other reasons are a resting heart rate that changes without cause. Cold hands and feet or unexplained weight gain count too. A family history of thyroid disease counts too.

Timing matters more than it does for testosterone. TSH is highest overnight and dips in the early afternoon. The variation reaches roughly 31 percent across a day. So give blood in the morning, and at around the same hour when repeating. That works out well, because testosterone follows the same rule.

Do not measure during or just after a spell of illness. Wait a few weeks after a period of severe sleep deprivation too. Both shift the axis.

Combine TSH with free T4 in the same draw. Does the complaint persist with a normal TSH and a normal free T4? Then free T3 can add information. With a persistently raised value, anti-TPO is the logical next step.