Low LH Levels in Transmale Individuals on Testosterone Therapy
Low LH levels in a transmale individual on testosterone therapy are an expected physiological response to exogenous testosterone administration and indicate appropriate negative feedback suppression of the hypothalamic-pituitary-gonadal axis. 1
Mechanism of LH Suppression
During exogenous testosterone administration, endogenous testosterone release is inhibited through feedback inhibition of pituitary luteinizing hormone (LH), and at large doses, spermatogenesis may also be suppressed through feedback inhibition of pituitary follicle-stimulating hormone (FSH). 1 This is the normal and expected pharmacological effect of testosterone therapy.
Clinical Significance in Transmale Patients
The degree of LH suppression correlates with treatment effectiveness in transmale individuals:
Less LH suppression is associated with inadequate masculinization. In transmale patients, the risk of not achieving desired body composition changes (such as increased lean body mass) is directly related to higher LH levels and lower testosterone levels. 2
For every standard deviation increase in LH, there is a 36% increased risk of failing to achieve expected body composition changes (OR: 1.36,95% CI: 1.01-1.83). 2
Conversely, for every standard deviation increase in testosterone levels, there is a 33% decreased risk of inadequate response (OR: 0.67,95% CI: 0.48-0.94). 2
Practical Interpretation
If LH remains elevated or inadequately suppressed in a transmale patient:
This suggests insufficient testosterone dosing or inadequate testosterone absorption/delivery. 2
The patient may experience suboptimal masculinization effects including inadequate changes in muscle mass, fat distribution, and other desired physical changes. 2
Dose adjustment should be considered to achieve both adequate testosterone levels and appropriate LH suppression. 2
Expected Suppression Patterns
The extent of LH suppression varies by testosterone formulation:
Long-acting injectable testosterone causes the most profound suppression (71.8% decrease in LH). 3
Intermediate-acting transdermal preparations (gels/patches) cause moderate suppression (59.2% decrease in LH). 3
Short-acting preparations cause less suppression (47.3% decrease in LH). 3
When to Investigate Further
Low LH with low testosterone requires additional evaluation. If a transmale patient has both low LH AND low testosterone levels (suggesting inadequate therapy or compliance issues), measure serum prolactin levels to screen for hyperprolactinemia. 4 Persistently elevated prolactin levels warrant endocrinology referral and evaluation for pituitary disorders including prolactinomas. 4
Common Pitfall
Do not confuse the expected LH suppression in transmale patients on testosterone therapy with pathological hypogonadism. In cisgender males with testosterone deficiency, low or low-normal LH combined with low testosterone indicates secondary (central) hypogonadism requiring investigation. 4 However, in transmale patients receiving exogenous testosterone, low LH with adequate testosterone levels is the desired therapeutic response. 1
The key distinction: Check the testosterone level. If testosterone is therapeutic and LH is suppressed, this is appropriate. If both are low, investigate compliance, absorption issues, or other pathology. 2