Endocrine Abstracts

JOINT2957

Background: Pituitary gigantism is a rare-yet important-disorder of GH axis leading to excessive height. It is usually due to over-secretion of GH by a pituitary adenoma occurring before epiphyseal closure. To date, several hematological diseases such as leukemia, thrombocytopenia, or Hodgkin lymphoma have been rarely reported in patients with pituitary adenoma, especially in acromegaly patients. The co-existence of the two diseases may be due to a common pathogenic mechanism or a co-incidence. However, the rarity of pituitary gigantism makes it difficult to establish the effect of elevated GH levels on platelet count.

Case Summary: A 14.75-year-old girl presented with increase in height noticed since 6 years and menorrhagia since 6 months. Her mid-parental height was 167.5 cm. Her parents were non-consanguineous and there was no family history of tall stature. At age 8 years, she was diagnosed with hypothyroidism (TSH 6.06 uIU/ml, fT4 1.59 ng/dl), and started on L-thyroxine 50mic daily. On examination, her weight was 72kg (+1.63SD), height 187cm (+3.72SD), and BMI 20.6 (+0.18SD). Her arm span was 182cm. She had normal blood pressure, left precordial bulge with an ejection systolic murmur heard over the base of heart. She had enlarged jaw, hands and feet. She had no ecchymotic patches, purpura, or cafe-au-lait spots. Her investigations revealed thrombocytopenia (platelets 52.000) which had been persistent in previous blood counts. Her IGF-1 level was normal (256 ng/ml), however, GH suppression test by glucose load was not suppressible (least 1.14 ng/ml). Her bone age was 14 years. She had hyperprolactinemia (67 ng/ml), while her TSH was 1.64 mIU/ml, Ft4 1.48 ng/dl on L-thyroxine treatment with negative thyroid antibodies. Lupus markers were done to exclude autoimmune cause of thrombocytopenia (ANA, C₃, and anti-dsDNA) and were negative. Serum cortisol, ACTH were normal. Her MRI brain showed left-sided pituitary microadenoma (3X4mm) and echocardiography revealed wide atrial septal defect with mildly hypertrophied prolapsed mitral valve with grade II-III regurgitation. Her fundus examination was normal. She was started on cabergoline 0.25 mg twice/week, and long-acting octreotide (lanreotide) 30mg monthly to suppress GH and prevent further increase in height. L-thyroxine was stopped as investigations confirmed TSH-secreting adenoma rather than a primary thyroid disorder. Her platelet count increased after receiving octreotide.

Conclusions: Understanding the link between pituitary gigantism and thrombocytopenia may shed light into the pathophysiology of the disease and requires further studies. Hence, performing complete blood count as routine work-up in patients with pituitary gigantism is essential.