Management of Hypergonadotropic Hypogonadism in Down Syndrome

Diagnosis

Elevated luteinizing hormone (LH) and follicle‑stimulating hormone (FSH) together with low testosterone indicate primary testicular failure in males with Down syndrome, confirming hypergonadotropic hypogonadism【1】【3】.
Increased estradiol in this population is attributed to peripheral aromatization of residual testosterone in adipose tissue【4】.
Low prolactin helps exclude hyperprolactinemia as a contributing cause【1】【5】.
Morning total testosterone (8–10 AM) should be measured with a reliable assay to confirm hypogonadism【6】【7】【8】.
If the first result is low, a second morning measurement on a different day is required to verify persistent deficiency【9】【4】.
For borderline total testosterone values, free testosterone by equilibrium dialysis and SHBG assessment are recommended【6】【4】.

Initiate therapy when morning total testosterone is consistently below ~300 ng/dL (clinical threshold)【7】.
Therapy is indicated when the patient exhibits symptoms that impair quality of life (e.g., reduced libido, erectile dysfunction, loss of body hair, low energy, decreased muscle mass, increased adiposity)【10】【2】.

Do not start testosterone if any of the following are present: breast or prostate cancer, prostate‑specific antigen (PSA) > 4 ng/mL (or > 3 ng/mL with high‑risk features), hematocrit > 50 %, untreated severe obstructive sleep apnea, uncontrolled heart failure, or a recent myocardial infarction or stroke within the past 6 months【9】【10】.

Route	Typical Regimen (adult male)	Source
Intramuscular (IM)	Testosterone enanthate or cypionate 75–100 mg weekly or 150–200 mg every 2 weeks	【7】
Transdermal gel	5–10 g of 1 % testosterone gel applied daily to non‑genital skin (hand washing required)	【7】
Transdermal patch	One to two 5‑mg patches applied nightly to back, thigh, or upper arm	【4】
Buccal tablet	30 mg tablet placed on buccal mucosa every 12 h	【4】

Target serum testosterone during treatment: mid‑normal adult range (≈ 400–700 ng/dL)【10】.

Re‑evaluate patients at 3–6 months after initiation, then annually【10】【5】.
At each visit: assess symptom improvement, adverse effects, and measure serum testosterone (aim 400–700 ng/dL; for IM formulations, draw ~1 week post‑injection)【10】【9】.
Check hematocrit; discontinue or reduce dose if > 54 %【5】.
Measure PSA in men > 40 years; refer to urology if PSA rises > 1.4 ng/mL within 12 months【10】【5】.
Monitor for gynecomastia, especially when estradiol elevation is present【3】【5】.

Fertility is typically severely impaired due to germ cell hypoplasia; testosterone therapy can further suppress spermatogenesis and should be avoided if fertility preservation is a goal【9】.
Semen analysis may be performed when fertility assessment is required【3】.
Genetic counseling is recommended given the underlying chromosomal abnormality【2】.

Screen for osteoporosis because bone mineral density is markedly reduced in this population and worsened by hypogonadism【7】.
Ensure adequate vitamin D supplementation【7】【8】.
Testosterone replacement has been shown to improve bone density【10】【9】.

Perform a comprehensive cardiovascular risk assessment before initiating therapy, as diabetes, hypertension, and dyslipidemia are more prevalent in Down syndrome【3】【5】.
In older men, testosterone therapy has been associated with increased coronary artery plaque volume; benefits must be weighed against potential vascular risk【7】【8】.

Do not treat asymptomatic individuals routinely; the benefit‑risk balance remains uncertain【7】【8】.
Do not rely solely on screening questionnaires for diagnosis; formal hormonal evaluation is essential【1】.
Always obtain a baseline hematocrit to detect polycythemia risk, especially with injectable formulations【5】.
Avoid routine estradiol measurement unless gynecomastia is present, as modest elevation is expected in this group【3】【5】.