This is with reference to the article “Serum prolactin levels in psoriasis and its association with disease activity: A case-control study” published by Keen et al.[1] This study, although carefully conducted, raised a few questions.

It is recommended that the blood sample for the estimation of prolactin (PRL) levels should be obtained without excessive venipuncture stress.[2] It is not known if such a precaution was taken.

The exclusion criteria employed in the study needs detailed scrutiny. A plethora of factors[2] can affect PRL levels, and studies on PRL estimation should carefully exclude these confounding factors to avoid overestimation and possible false association.

  1. Known cases of renal, hepatic, endocrinopathy (prolactinoma and hypothyroidism) or psychiatric disease were excluded, but it is not specified whether screening tests such as thyroid function tests were done. Pretesting before inclusion is essential because clinical features of thyroid disease are often non-specific; hence, history and clinical examination are not sufficient to rule out hypothyroidism.
  2. The author’s exclusion criteria, although exhaustive, miss out on a few drugs known to cause hyperprolactinemia, such as oral contraceptive pills, and anticonvulsants[2]
  3. Stress being an established exacerbating factor for psoriasis is also known to increase PRL levels.[2] Psychiatric comorbidity in psoriasis is well known, and although known cases of the psychiatric disease were excluded, some of them may be undiagnosed cases of depression or anxiety which could have caused an overestimation of PRL levels
  4. Control for physiological confounding factors such as coitus or exercise, which could cause PRL elevation appears to be poor.[2,3] History of coitus on the night prior to sample collection and history of exercise on the morning of sample collection was not elaborated.

Even though monomeric 23 kDa form of PRL is the predominant form, its big variants (50 and 150 kDa) known as “big prolactin” or macroprolactin represent dimers, trimers, polymers of PRL, or prolactin–immunoglobulin immune complexes (PRL–IgG complexes),[3] which remain reactive to varying degrees in all PRL immunoassays. Interestingly, they exhibit little, if any, biological activity in vivo and consequently its presence is considered clinically irrelevant.[4,5] In this study, levels of PRL were quantitatively estimated using an electro-chemiluminescence immunoassay (ECLIA).[1] Though generally robust and reliable, such immunoassays are susceptible to interference from PRL–IgG autoantibody complex or macroprolactin.[5] Polyethene glycol precipitation is an inexpensive way to detect the presence of macroprolactin in the serum.[3] All sera subjected to PRL estimation should be sub-fractionated using polyethene glycol precipitation to provide a more meaningful clinical measurement of the bioactive monomeric PRL content.[5]

The patients received topical treatment for 6 weeks following which reduction in the PRL levels was observed, but post-treatment PASI scores were not reported. In addition, it is not specified as to what treatment was prescribed. Topical corticosteroids are still a popular choice of topical treatment for psoriasis. A literature search showed no studies evaluating the effect of topical steroids on PRL levels. Nevertheless, it is noteworthy that studies have shown a reduction in PRL secretion or levels following systemic steroids. If steroids were applied over larger areas, consequent systemic absorption might have affected PRL levels.


1. Keen MA, Hassan I. Serum prolactin levels in psoriasis and its association with disease activity: A case-control study. Indian J Dermatol. 2014;59:562–6. [PMC free article] [PubMed]2. Melmed S, Casanueva FF, Hoffman AR, Kleinberg DL, Montori VM, Schlechte JA. Diagnosis and treatment of hyperprolactinemia: An Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96:273–88. [PubMed]3. Majumdar A, Mangal NS. Hyperprolactinemia. J Hum Reprod Sci. 2013;6:168–75. [PMC free article][PubMed]4. Biller BM, Luciano A, Crosignani PG, Molitch M, Olive D, Rebar R, et al. Guidelines for the diagnosis and treatment of hyperprolactinemia. J Reprod Med. 1999;44(Suppl 12):1075–84. [PubMed]5. Fahie-Wilson M, Smith TP. Determination of prolactin: The macroprolactin problem. Best Pract Res Clin Endocrinol Metab. 2013;27:725–42. [PubMed]