Signs and Symptoms of Hormonal Hypersecretion in Pituitary Microadenomas
The clinical presentation of hormonal hypersecretion from a 6 mm microadenoma depends entirely on which hormone is being overproduced, with prolactinomas, growth hormone-secreting adenomas, and ACTH-secreting adenomas each causing distinct, recognizable clinical syndromes that require specific biochemical evaluation. 1, 2, 3
Prolactin-Secreting Microadenomas (Prolactinomas)
Prolactinomas account for 32% to 66% of all pituitary adenomas and present with sex-specific symptoms 3:
In women:
- Amenorrhea or oligomenorrhea 3
- Galactorrhea (inappropriate breast milk production) 3
- Loss of libido 3
- Infertility 3
In men:
Biochemical evaluation: Measure serum prolactin levels, which will be elevated; levels typically correlate with tumor size 2, 3
Growth Hormone-Secreting Microadenomas
Growth hormone-secreting tumors account for 8% to 16% of pituitary adenomas 3, 4:
Physical features of acromegaly:
- Enlargement of hands and feet (acral enlargement) 3, 5
- Coarsening of facial features with enlargement of lips, tongue, and nose 3
- Frontal bossing and prognathism (jaw protrusion) 3
- Skin changes including increased skin tags and oily skin 3
- Joint pain and arthropathy 3
Metabolic manifestations:
- Hyperphosphatemia (elevated serum phosphate from increased renal tubular reabsorption) 5
- Glucose intolerance or diabetes mellitus 3
- Hypertension 3
Biochemical evaluation: Elevated insulin-like growth factor 1 (IGF-1) levels and failure of growth hormone suppression during oral glucose tolerance test 3, 5
ACTH-Secreting Microadenomas (Cushing Disease)
ACTH-secreting tumors account for 2% to 6% of pituitary adenomas and cause Cushing disease 3, 6:
Classic features of hypercortisolism:
- Central obesity with buffalo hump and supraclavicular fat pads 3
- Moon facies (rounded facial appearance) 3
- Purple striae (wide, violaceous stretch marks) 3
- Easy bruising and thin skin 3
- Proximal muscle weakness 3
- Hypertension 3
- Hyperglycemia or diabetes mellitus 3
- Psychiatric symptoms including depression and mood lability 3
- Menstrual irregularities in women 3
- Osteoporosis 3
Biochemical evaluation: Late-night salivary cortisol is the best screening test; 24-hour urinary free cortisol and overnight 1 mg dexamethasone suppression test are also used 1, 3
TSH-Secreting Microadenomas
TSH-secreting tumors account for only 1% of pituitary adenomas 3:
Features of hyperthyroidism:
- Weight loss despite increased appetite 3
- Heat intolerance and excessive sweating 3
- Tremor and anxiety 3
- Palpitations and tachycardia 3
- Goiter (thyroid enlargement) 3
Biochemical evaluation: Elevated free T4 and T3 with inappropriately normal or elevated TSH 3
Important Clinical Considerations
Even microadenomas as small as 6 mm can cause significant hormonal hypersecretion requiring treatment, though mass effects and hypopituitarism are uncommon at this size. 1, 7, 8
Key diagnostic pitfalls to avoid:
- In children and adolescents, symptoms may be subtle or attributed to normal developmental changes, leading to delayed diagnosis 1
- Pubertal delay, amenorrhea, or rapid growth velocity in young patients should prompt evaluation for pituitary adenoma 1
- Microadenomas rarely cause visual field defects or other mass effects, so their absence does not exclude the diagnosis 1, 7
Complete hormonal assessment is essential even when one hormone excess is suspected, as mixed adenomas can secrete multiple hormones 1, 2, 6