SUN-199 - When Weight Gain Speaks Louder than Symptoms: A Silent Macroprolactinoma with Extreme Hyperprolactinemia ( >8,000 Ng/Ml) in an Adolescent

Background
Prolactinomas are uncommon in the pediatric population. In premenarchal girls, classic symptoms such as galactorrhea or amenorrhea may be absent, which can delay diagnosis. Beyond reproductive suppression, hyperprolactinemia has been linked to metabolic alterations, including weight gain and insulin resistance.

Case Presentation
A 13-year-old girl was referred for evaluation of progressive, unexplained weight gain despite adherence to healthy diet recommendations and regular physical activity. Her growth chart showed progressive weight gain since age 10 years, with a decline in height percentile from the 90th to the 80th percentile over the preceding year. Puberty had begun at age 10 years with thelarche but had progressed slowly, and she remained premenarchal. On history, she denied galactorrhea, headaches, or visual changes. Physical examination revealed Tanner stage II-III breast development with lipomastia and acanthosis nigricans. Initial laboratory workup demonstrated normal thyroid function, IGF-1, karyotype (46,XX), hemoglobin A1c, and negative screening for Cushing syndrome.

At follow-up six months later, growth velocity and pubertal progression had stalled. Repeat evaluation showed a mildly elevated hemoglobin A1c (5.8%), suppressed gonadotropins (LH 0.08 mIU/mL, FSH 0.28 mIU/mL) with low estradiol ( < 10 pg/mL), suppressed gonadotropins with low estradiol ( < 10 pg/mL), and marked hyperprolactinemia (>8,000 ng/mL). Pituitary MRI identified a 2 × 3.4 × 2.5 cm sellar and suprasellar mass with left cavernous sinus invasion and pituitary stalk deviation, consistent with a macroprolactinoma. Ophthalmologic assessment was normal. Cabergoline therapy was initiated with rapid dose escalation, leading to symptomatic improvement, decline in serum prolactin, and tumor shrinkage. On follow-up six months later, gonadotropins had recovered.

Discussion
This case highlights an atypical presentation of macroprolactinoma in adolescence. The absence of galactorrhea or neurological symptoms can obscure diagnosis when hyperprolactinemia develops before full pubertal maturation. Elevated prolactin suppresses gonadotropin-releasing hormone(GnRH) secretion, resulting in hypogonadotropic hypogonadism and stalling of pubertal progression. Moreover, prolactin excess exerts metabolic effects through reducing dopaminergic tone, enhancing adipogenesis, and impairing insulin sensitivity manifesting clinically as weight gain and acanthosis nigricans. A high index of suspicion should be kept in the evaluation of prepubertal child with delayed growth and puberty, as classical hormonal symptoms may be absent. These findings underscore that macroprolactinomas can present with metabolic and growth disturbances accompanied by stalled pubertal progression, even in the absence of galactorrhea or neurological symptoms.

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