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RESOLUTION OF A HYPERPROLACTINEMIA IN A WESTERN LOWLANDGORILLA (GORILLA GORILLA GORILLA)Author(s): Jenifer ChatfieldD.V.M., Lily ZhangPh.D., Jacques RameyM.D., Ph.D., Todd BowsherPh.D.,Naida LoskutoffPh.D., and Kortney O'NeillD.V.M.Source: Journal of Zoo and Wildlife Medicine, 37(4):565-566. 2006.Published By: American Association of Zoo VeterinariansDOI: http://dx.doi.org/10.1638/06-050.1URL: http://www.bioone.org/doi/full/10.1638/06-050.1

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Journal of Zoo and Wildlife Medicine 37(4): 565–566, 2006Copyright 2006 by American Association of Zoo Veterinarians

RESOLUTION OF A HYPERPROLACTINEMIA IN A WESTERNLOWLAND GORILLA (GORILLA GORILLA GORILLA)

Jenifer Chatfield, D.V.M., Lily Zhang, Ph.D., Jacques Ramey, M.D., Ph.D., Todd Bowsher, Ph.D.,Naida Loskutoff, Ph.D., Kortney O’Neill, D.V.M.

Abstract: Prolactin-secreting pituitary adenomas are one of the most common causes of infertility in women. Pro-lactin plays an important role in lactation and is involved in producing some of the normal mammalian breeding andmaternal behaviors. Elevated serum prolactin concentrations can adversely affect the reproductive cycle in females byinhibiting the normal lutenizing hormone surge that stimulates ovulation. A 17-year-old western lowland gorilla (Gorillagorilla gorilla) presented with low fertility and hyperprolactinemia. An MRI confirmed a pituitary mass and treatmentwas initiated with cabergoline. Following 8 mo of treatment, mass size decreased and serum prolactin was withinnormal limits. The gorilla began to engage in normal breeding behavior, and within 6 mo of completing treatment,was pregnant. Hyperprolactinemia, secondary to presumed microprolactinoma, may be more common among breeding-age gorillas than is currently diagnosed and in humans is an easily diagnosed and treatable condition.

Key words: adenoma, cabergoline, gorilla, prolactin, reproduction.

BRIEF COMMUNICATION

Pituitary adenomas are one of the most commoncauses of infertility in women. Because of the pi-tuitary gland’s role in the regulation of prolactinsecretion, a prolactin-secreting adenoma (prolacti-noma) adversely affects ovulation and the regular-ity of the reproductive cycle. Prolactin plays a largerole in the regulation of lactation and affects breed-ing and some maternal behavior.3 These tumors canremain clinically silent until their size becomes suf-ficient to cause visual field deficits or severe head-aches.1 Thus, the majority may go undiagnosed dueto insubstantial clinical signs. Prolactinomas maybe treated medically or surgically with microade-nomas (�10 mm) generally treated medically for6–12 months. The following case report describesthe first confirmed antemortem diagnosis and suc-cessful treatment of a hyperprolactinemia in a west-ern lowland gorilla, Gorilla gorilla gorilla.

A 17-year-old, primiparous western lowland go-rilla presented with decreased libido and low fer-tility compared to her female siblings. Menstrualcycle was very regular as determined by daily urinecollections evaluated for presence of blood (Hema-Combistix, Bayer Corporation, Elkhart, Indiana

From the Gladys Porter Zoo, Brownsville, Texas 78520,USA (Chatfield, O’Neill); the Texas Center for Reproduc-tive Health, Dallas, Texas 75246, USA (Zhang); the Heart-land Center for Reproductive Medicine, Omaha, Nebraska68138, USA (Ramey); the Dallas Zoo, Dallas, Texas75203, USA (Bowsher); and Omaha’s Henry Doorly Zoo,Omaha, Nebraska 68107, USA (Loskutoff). Present ad-dress (Chatfield): Tampa’s Lowry Park Zoo, 1101 W.Sligh Avenue, Tampa, Florida 33604, USA. Correspon-dence should be directed to Dr. Chatfield.

46515, USA). Urinary progesterone and estrogenwere monitored using a standard ELISA. Physicalexam, complete blood count, and serum biochem-ical profile were within normal limits for the spe-cies.2

Following two failed embryo transfers under se-dation, a hormonal profile was performed on freshserum (Texas Center for Reproductive Health, Dal-las, Texas 75246, USA). Serum prolactin was 302ng/ml (reference range for humans 1.9–25 ng/ml).Banked serum samples revealed that the prolactinhad been abnormally elevated for several months.An MRI was performed and revealed a pituitarymass consistent with a microadenoma (�10 mm)involving the pituitary stalk as well as diffuse en-largement of the pituitary gland.

Consistent with clinical signs and imaging find-ings, treatment was initiated with cabergoline (Dos-tinex, Pfizer Inc., New York, New York 10017,USA) 0.25 mg (0.002 mg/kg) p.o. twice weekly).Prolactin concentrations remained elevated (68.7ng/ml) 3 mo later, so the dose was increased to 0.5mg (0.004 mg/kg) p.o. twice weekly. After 6 mo,prolactin concentrations were within normal limits(10.4 ng/ml), and an MRI confirmed that the masswas notably smaller. Treatment was discontinued.Subsequently, the gorilla was seen copulating reg-ularly and within 6 mo of concluding the treatment,the gorilla was pregnant.

Hyperprolactinemia is one of the most commonendocrine disorders of the hypothalamic–pituitaryaxis in young women4,5 and may present with avariety of symptoms including hypogonadism,amenorrhea or galactorrhea.1,4,5 Hyperprolactinemiais often clinically silent; thus the condition’s prev-alence in humans is difficult to establish.1 The most

566 JOURNAL OF ZOO AND WILDLIFE MEDICINE

common cause of hyperprolactinemia is a prolac-tinoma.1 In addition, hyperprolactinemia can resultdue to the reduced elimination of prolactin by theliver or kidney, or from the administration of anti-psychotic drugs, hypothyroidism, and physiologicstress.

This case has an atypical presentation becausenormal, regular menses were confirmed in the faceof elevated prolactin. Once the hyperprolactinemiawas discovered, many of the usual causes were dis-counted with physical examination and blood tests.Hypothyroidism was eliminated based on normalTSH (3.16 ng/ml, reference range for humans 0.4–4.0 ng/ml) in conjunction with elevated serum pro-lactin. Organ disease was eliminated based on anormal complete blood count and serum biochem-ical profile. The gorilla was a classic presentationfor clinically silent microadenoma based on herage, overall good health status, and low fertilitywhen compared to her female siblings.

Treatment of hyperprolactinemia secondary topituitary microadenomas is generally done withbromocriptine or, more recently, cabergoline orquinagolide.1 Cabergoline offers the advantage oftwice-weekly dosing as opposed to daily dosingand fewer side effects than with either bromocrip-tine or quinagolide. Cabergoline is a dopamine ag-onist with a high affinity for D2-type receptors. Theresulting elevated dopamine concentrations act asnegative feedback to the pituitary gland, decreasingthe production of prolactin. No adverse side effects

of cabergoline administration were noted in thiscase but could include nausea, dizziness, hypoten-sion, syncope, or abdominal pain.

Prolactinoma-induced hyperprolactinemia iscommon among young women with low fertilityand may be more common among breeding-age go-rillas than is currently diagnosed. A survey of se-rum prolactin concentrations in the captive gorillapopulation would be necessary to determine theprevalence of this condition. Fortunately, following8 mo of treatment and a repeated MRI, serum pro-lactin indicated that the hyperprolactinemia in thiscase was controlled. The subsequent pregnancyconfirmed successful treatment.

LITERATURE CITED

1. Crosignani, P. G. 2006. Current treatment issues infemale hyperprolactinemia. Eur. J. Obstet. Gynecol. Re-prod. Biol. 125: 152–164.

2. Loomis M. R. 2003. Great apes. In: Fowler, M. E.,and R. E. Miller (eds.). Zoo and Wild Animal Medicine,5th ed. W. B. Saunders Co., Philadelphia, Pennsylvania.Pp. 385–386.

3. Freeman, M. E., B. Kanyicska, A. Lerant, and G.Nagy. 2000. Prolactin: structure, function, and regulationof secretion. Physiol. Rev. 80: 1523–631.

4. Luciana, A. A. 1999. Clinical presentation of hyper-prolactinemia. J. Reprod. Med. 44: 1085–90.

5. Mah, P. M., and J. Webster. 2002. Hyperprolactin-emia: etiology, diagnosis, and management. Semin. Re-prod. Med. 20: 365–74.

Received for publication 10 June 2006