Endocrine Abstracts

Background

Data on clinical characteristics and natural history of patients with non-functioning pituitary microadenomas (NFPmA) is limited to small-scale studies.

Methods

A retrospective evaluation of initial clinical presentation and natural history of patients with NFPmA (conservatively managed, years; 2004–2020) was undertaken. Initial symptoms, tumor size, and pituitary function were assessed. Exclusion criteria; surgery, radiation, dopamine agonists, pregnancy, radiologic findings of Rathke’s cleft cyst. Patients on thyroid, glucocorticoid, sex hormone replacement, chronic opioids, or with traumatic brain injury were excluded from pituitary function analysis. Tumor size change ≥2 mm on pituitary MRI in any dimension was considered significant. SPSS was used for descriptive statistics, and STATA for incidence.

Results

A cohort of 262 patients with NFPmA (age 41.6±15.2 years; 64.9% female) was studied. Fatigue (77.1%) and headache (69.5%) were the most common presenting symptoms. Mean largest tumor dimension was 4.6±1.9 mm; 53% were <5 mm and 47% were 5–9 mm. Patients were taking thyroid (for primary hypothyroidism; 21.0%), 5.3% glucocorticoid, 2.7% growth hormone replacement, 0.4% desmopressin; 38.5% of females estrogen/progesterone and 22.1% of males testosterone. In patients with fully evaluable pituitary function, 94.5% had no deficiencies, 4.0% deficiency in 1-axis, and 1.5% in 2-axes (most commonly hypogonadism; 4.7% and growth hormone deficiency; 1.9%), 9.2% had drug-related and 1.5% transient hyperprolactinemia. During median MRI follow-up of 19 months, 8.7% of tumors grew, 38.5% shrunk, and 52.8% were stable. Growth incidence was 2.3/100 person-years (PYs) with a mean time-to-growth of 41.6±38.9 months. Tumors <5 mm and 5–9 mm showed no difference in growth. Tumor growth did not vary by sex. Mean time-to-growth was lower in patients ≥65 vs <65 years (14.5±7.9 vs 49.9±41.0 months, P = 0.01).

Discussion

Previous reported pituitary deficiency in patients with NFPmA ranges from 0 to 42%; our findings are on the lower end of this estimate. Interestingly, incidence of linear growth in our study was lower than volumetric growth in a previous study (2.3 vs 5.0/100 PYs), but percentage of enlarging microadenomas (8.7%) was similar to previously reported values (7.4–12.5%).

Conclusions

This is the largest single-center study of NFPmA with uniform clinical assessment and follow-up. Patients frequently reported fatigue and headache, without significant pituitary dysfunction. Enlarging tumors were rare and not associated with visual deficits or new hypopituitarism. Since time-to-growth was longer in younger patients, extending follow-up MRI timeline for microadenomas from current recommendations to up to 3-years in patients <65 years of age should be considered.