Table 5. T Therapy options.

Formulation	Route of administration	Frequency of administration	Advantages	Disadvantages
Testosterone 1% 1.62% and 2% gel available	Transdermal	Applied daily to upper arms or lower abdomen requires dose titration Daily	Fast onset. Levels peak 2–4 hours after application then gradually fall to very low levels before the next application	Skin irritation at application site Potential for interpersonal transfer, partner or child Non-compliance long-term especially with hot climate, swimming etc.
5% testosterone cream			Small volume applied to scrotum application	Licensed in Australia and for import into UK.
Testosterone undecanoate	Oral capsules	Once or twice daily	Lymphatic absorption reduces liver involvement	Levels fluctuate, lower efficacy. Normal serum T level attained for only up to 3–5 hours Daily/twice daily commitment Must be taken with food
Testosterone undecanoate	Intramuscular injection. Injected slowly deep into the gluteal muscle. The second injection (loading dose) is given at 6 weeks, and the third dose 12 weeks after the second. Injection interval is adjusted based on trough total T level just before the third injection, aiming for the lower end of normal reference range level. Monitor trough total T and FBC every 3–5 injections or annually	Every 10–14 weeks adjusted to maintain trough T >12 nmol/L	Steady state levels Reduced frequency of administration improves compliance. Patient compliance less of a problem	Long duration of action prevents drug withdrawal in the event of adverse side-effects. Pain, discomfort and adverse reaction at injection site. Requires large muscle bulk for injection. Lifestyle restrictions as it cannot be self‐administered. Rare AE of POME presenting with severe coughing episode during injection. Longer recovery period after therapy cessation
Testosterone enanthate	Intramuscular injection	Every 2–3 weeks. Dose flexibility and convenient administration, relatively inexpensive. Improves symptoms of androgen deficiency; mostly noticeable in the first days after the injection. SC injection has comparable pharmacokinetics, safety and tolerability to IM injection and can be self‐injected.	Short duration of action allows drug withdrawal if there are adverse side effects	Levels fluctuate potentially unpleasant “peak & trough” symptoms due to supraphysiological T levels post-injection which decline to hypogonadal range prior to the next injection. Polycythaemia due to supraphysiological T levels. Pain, discomfort at injection site. Lifestyle restrictions for patients not self‐injecting
Testosterone cypionate	Intramuscular injection (also subcutaneous micro-dosing)	Every 1–4 weeks	Medium/short duration	Little long term published data
Testosterone propionate	Intramuscular injection	Currently available as one of four testosterone esters used in Sustanon 250, which is usually administered every 3 weeks. Sustanon’s long duration of action prevents drug withdrawal in the event of adverse side-effects

T: testosterone, FBC: full blood count, POME: pulmonary micro-embolism.

Data from Hackett et al (Int J Clin Pract 2017;71:e12901) and Jayasena et al (Clin Endocrinol [Oxf] 2022;96:200-19) [114].