From the Guidelines
Yes, sex hormone-binding globulin (SHBG) levels can be decreased in patients with pituitary adenomas, particularly those that secrete growth hormone (GH) or prolactin.
Background
This decrease occurs because these hormonal imbalances affect liver production of SHBG. In growth hormone-secreting adenomas (acromegaly), excess GH and IGF-1 can directly suppress SHBG synthesis in the liver, as suggested by the relationship between GH levels and IGF1 concentrations 1.
Clinical Significance
Similarly, prolactinomas can lead to hypogonadism with reduced estrogen levels, which normally stimulate SHBG production. The decreased SHBG is clinically significant because it increases free (bioavailable) testosterone and estrogen in circulation, potentially causing symptoms like menstrual irregularities in women or altered sexual function in both sexes.
Diagnosis and Management
Treatment of the underlying pituitary adenoma through surgery, medication (such as dopamine agonists for prolactinomas or somatostatin analogs for GH-secreting tumors), or radiation therapy typically helps normalize SHBG levels as the hormonal environment returns to balance. According to the consensus guideline for the diagnosis and management of pituitary adenomas in childhood and adolescence, dynamic pituitary assessment of possible hypofunction and hyperfunction of other anterior pituitary hormones is recommended 1.
Key Considerations
Key considerations in managing pituitary adenomas include:
- Monitoring GH and IGF1 levels at baseline and during follow-up 1
- Assessing for hypofunction of other pituitary hormones caused by tumour mass compression or prolactin co-secretion 1
- Evaluating for syndromic diseases associated with pituitary adenomas, such as Carney complex, McCune–Albright syndrome, and MEN1 or MEN1-like disease 1
- Offering biochemical screening for pituitary hormone excess to all CYP with these syndromes 1
From the Research
SHBG Levels in Pituitary Adenoma
- The relationship between Sex Hormone Binding Globulin (SHBG) levels and pituitary adenoma is complex, with some studies suggesting that SHBG can be affected by the presence of a pituitary tumor 2.
- In one case study, a patient with a TSH-secreting pituitary adenoma was found to have elevated SHBG levels, which supported the diagnosis of TSHoma 3.
- However, there is no direct evidence to suggest that SHBG levels can be decreased in pituitary adenoma, and more research is needed to fully understand the relationship between SHBG and pituitary tumors.
Factors Affecting SHBG Levels
- SHBG levels can be influenced by various factors, including metabolic diseases, endocrine disorders, and certain medications 2.
- Body mass index (BMI) and insulin-like growth factor 1 (IGF-1) levels have been identified as potential risk factors for discordant GH and IGF-1 levels after pituitary surgery in acromegalic patients 4.
- The primary treatment of acromegaly, including transsphenoidal adenomectomy and medical management with dopamine agonists and somatostatin analogs, can also impact SHBG levels 5, 6.
Clinical Significance of SHBG
- SHBG has been recognized as a useful clinical marker for certain pathological states, including obesity, metabolic syndrome, and polycystic ovary syndrome 2.
- Further research is needed to fully understand the clinical significance of SHBG and its potential role in the diagnosis and management of pituitary adenoma and other endocrine disorders.