Does Mirena Elevate Prolactin?
No, the levonorgestrel-releasing intrauterine system (Mirena) does not clinically elevate serum prolactin levels in reproductive-aged women. The systemic levonorgestrel exposure from Mirena is extremely low (4-13% of combined oral contraceptives), and the available evidence shows no association between intrauterine levonorgestrel delivery and hyperprolactinemia 1, 2.
Systemic Hormone Exposure from Mirena
Mirena releases only 20 micrograms of levonorgestrel per 24 hours directly into the uterine cavity, resulting in minimal systemic absorption 3.
Plasma levonorgestrel concentrations in Mirena users average 147±59 pg/mL, which is substantially lower than levels achieved with oral contraceptives or other systemic progestin methods 2.
Systemic levonorgestrel levels decline over time, from approximately 191 pg/mL in the first year to 117-133 pg/mL by years 6-8, yet remain detectable and therapeutically effective 2.
Evidence on Prolactin Effects
A 1995 study measuring prolactin levels in women after 6 years of Mirena use found no elevation in serum prolactin, with the contraceptive mechanism primarily acting locally on the endometrium rather than through systemic hormonal suppression 4.
Oral contraceptives containing ethinyl estradiol and levonorgestrel can increase prolactin and macroprolactin levels, but this effect is attributed to the estrogen component and systemic progestin exposure—neither of which apply to the intrauterine levonorgestrel system 5.
The KDIGO 2025 guidelines note that systemic exposure with levonorgestrel-releasing IUDs is only 4-13% of that with combined oral contraceptives, making clinically significant prolactin elevation highly unlikely 1.
Clinical Implications
If a woman with Mirena presents with hyperprolactinemia, the IUD is not the cause—investigate other etiologies including medications (antipsychotics, metoclopramide), hypothyroidism, pituitary adenoma, or physiologic stress 6.
Mirena is actually a preferred contraceptive option for women who need to avoid estrogen, including those with cardiovascular risk factors or conditions where estrogen-related prolactin stimulation would be problematic 3.
The progestin-only nature of Mirena makes it suitable for women with polycystic liver disease (PLD) in ADPKD, where estrogen exposure may worsen cyst progression, further supporting its minimal systemic hormonal effects 1.
Common Pitfalls to Avoid
Do not attribute mild hyperprolactinemia to Mirena use—the intrauterine delivery system does not produce the systemic progestin levels necessary to affect prolactin secretion 2, 4.
Do not remove a Mirena IUD in response to an incidental finding of elevated prolactin—pursue standard hyperprolactinemia workup including medication review, thyroid function testing, and pituitary imaging if indicated 6.
Distinguish between oral levonorgestrel contraceptives and the intrauterine system—only systemic progestin formulations combined with estrogen have been shown to affect prolactin levels 5.