Excerpts: Guidance for Prolactin Monitoring and Elevated Prolactin Levels in Transfeminine People

By Aly | First published March 11, 2020 | Last modified September 24, 2021

Notice: This page was originally posted as a thread on Reddit and has not yet been properly or fully revised since being moved to Transfeminine Science.


Iwamoto et al. (2019)

Iwamoto, S. J., Defreyne, J., Rothman, M. S., Van Schuylenbergh, J., Van de Bruaene, L., Motmans, J., & T’Sjoen, G. (2019). Health considerations for transgender women and remaining unknowns: a narrative review. Therapeutic Advances in Endocrinology and Metabolism, 10, 2042018819871166. [DOI:10.1177/2042018819871166]:

Prolactinoma in [transgender women] has also been reviewed and associated with high-dose [cyproterone acetate].189 While the recent Endocrine Society guidelines18 suggest periodic monitoring of serum prolactin, a downgraded recommendation from the previous rendition, future studies will help us determine whether routine prolactin screening is needed particularly in [transgender women] who do not take [cyproterone acetate]. Defreyne and colleagues195 revealed that [cyproterone acetate] increased prolactin levels in [transgender women] but the levels decreased when [transgender women] discontinued [cyproterone acetate]. Fung and colleagues117 demonstrated higher prolactin levels in [transgender women] receiving [cyproterone acetate] than those taking spironolactone. Given these newer data, we recommend checking prolactin only in those patients with signs or symptoms of hyperprolactinaemia before or after starting feminizing [gender-affirming hormone therapy].

Callen-Lorde (2018)

Callen-Lorde Community Health Center (2018). Protocols for the Provision of Hormone Therapy. [URL] [PDF]:

Elevated Prolactin Level

If a patient has a prolactin level between 20 and 100 ng/mL, the patient should be followed with history (focusing on visual field deficits, headaches) and physical exam (blood pressure, fundoscopic exam and gross visual field assessment). For prolactin levels 40-100 ng/mL, reduce estrogen levels by half and recheck in 6-8 weeks. Continue hormones at the lower dose if prolactin levels remain under 40ng/mL. If a patient has a prolactin level over 100ng/mL, hormones should be discontinued, and the level should be rechecked. If it remains over 100ng/mL, an MRI of the pituitary should be obtained to rule out pituitary adenoma. If the MRI is normal, hormones can be restarted at a lower dose, and prolactin level should be followed. If it continues to rise, or if the MRI is abnormal, the patient should be referred to an endocrinologist.

Guidelines for Elevated Prolactin Level

Level (ng/mL)Level (mIU/L)Action
<25<530Continue to monitor per protocol.
25–40530–850Ask patient about outside sources of estrogen and continue to monitor per protocol.
40–100850–2100Decrease estrogen dose by half and recheck in 6–8 weeks.
>100>2100Stop estrogen and recheck in 6–8 weeks. If levels remain high, MRI pituitary. If level decreases, restart estrogen at lower dose.

Adapted from Whitman Walker Transgender Protocols 2010.

Note: Added a column for mIU/L prolactin levels in the table above.

Additional Notes

Estradiol and progesterone act synergistically to increase prolactin levels in monkeys (Williams et al., 1981; Williams et al., 1985).