What you are describing sounds like typical male pattern hair loss. There are at least 27 identified genes that contribute to this kind of hair loss, also known as androgenetic alopecia. It is well known that patterned hair loss is 'polygenic' i.e. if you inherit MORE of those genes, the more likely you are to encounter this condition.
From your description, you may belong to a subfamily of male patterned hair loss called 'anterior recession' (not a formal term). You can have a look at the Norwood-Hamilton scale that describes the progression of hair loss in men. While you are still young, the description you present sounds like the subtypes with an 'A' following the scale number.
This condition is typically caused by 2 main factors - genetics and the strong male hormone, DHT or dihydrotestosterone. Other contributory factors include - stress, poor diet, concurrent medical conditions, certain medications etc.
A physical examination and especially a high magification trichoscopy / dermoscopy should be performed to assess the degree of miniaturization to customise a treatment that is suitable to you.
The blood tests that I MAY be performing include Zinc, Copper, Full blood counts and Ferritin, HIV serology, Hep B - in preparation for a hair transplant.
There is no value in testing for testosterone or DHT as levels of these hormones may fluctuate across the day and will not change the treatment of the problem (not to mention that DHT levels is an expensive test to run).
I adopt a comprehensive and logical strategy to tackle this problem and is done concurrently or in a step wise order.
1. STOP further hair loss
2. OPTIMIZE existing fine and thin hairs (reverse miniaturization)
3. RESTORE hair that has already been lost i.e. dormant follicles along the hair line (or elsewhere)
It is great that you have researched on treatments available to you and you have correctly identified the main FDA-approved treatments available for male pattern hair loss. Depending on the the degree of fine, miniaturized hair along your hairline, finasteride and minoxidil may or may not work to reverse the process of a receding hairline.
85% of men respond to finasteride and show an average increase in 17-20% in terminal hair counts i.e thickening of existing hairs. (Dr Gupta et al 2018) Side effects of this medication are often overstated on the internet - the risk of 'sexual' side effects range between 1-3% depending on which journal you read - European or American. The 'sexual' side effects were reported as reversible in all but ONE paper [published by an Endocrinology (a specialty that deals with hormones) journal].
Latest studies shows that when administered finasteride 1mg vs a placebo (sugar pill), there was no statistical difference in the number of men who reported 'sexual' side effects.
A hair restoration procedure (some doctors call this a hair transplant) is the only means to replace hair loss along the hair line reliably. The degree of restoration will depend on a few factors - the rate of hair loss, your age, the availability of 'donor follicles' and whether or not you go on medication to prevent further hair loss.
Some people do not react well to finasteride or minoxidil - libido issues, erectile dysfunction, migraines, giddiness etc.
There are regenerative medicine options such as Regenera Activa that can stop hair loss and thicken existing fine hairs, including along the hair line - before and after photos can be shown to you during a consultation.
Certain supplements that have gone through rigorous research use herbal supplements to counter the effects of DHT - the most famous being Tumeric extract (Cucurmin) and Saw Palmetto. These ingredients are found in a hair restoration nutraceutical (supplement) called Nutrafol for Men. These are known to not only not affect libido negatively, but to support good sexual and prostate health.
Once either of these medications, nutraceuticals, regenerative medicine solutions have stabilized your hair loss condition, we would consider TARGET 3: RESTORING the receding hairline to frame your face to aesthetic proportions.
Seek out a (few) clinic(s) that has a strong focus and experience in hair restoration who are able to assess your condition and explain to the process to you in detail, counsel you on hair restoration options and give you a realistic expectation of what to expect, considering your young age.
I hope this helps.
Dr Joshua Chong